Endometrial Cancer. The evolving role of adjuvant radiation therapy

Patricia J. Eifel


During the past 15 years, there have been a host of trials published that attempt to define the indications for external beam radiation therapy and brachytherapy in patients with varying risk factors for recurrence after hysterectomy for endometrial cancer. Although these trials have helped to define a group of relatively low-risk cancers that clearly do not require adjuvant treatment, the roles of radiation therapy, chemotherapy, and lymphadenectomy are still subjects of considerable controversy. In this lecture, some of the factors that have contributed to these ambiguities will be discussed as will some practical suggestions for how the current data and guidelines can be used to make difficult decisions about individual cases. Although the technical aspects of radiation therapy delivery are less challenging than for some other gynecologic cancers, possible methods for optimizing therapeutic ratio with IMRT and brachytherapy technique will be discussed.


Cervical Cancer

Patricia J. Eifel


Brachytherapy plays a critical role in the curative management of locally advanced cervical cancers. Although the ability to cure even very advanced cancers is in part thanks to the tendency of HPV-related cancers to remain loco-regionally confined and to the introduction of effective concurrent chemotherapy, the ability to use the uterus as a container for radioactive sources has been recognized for more than 100 years as a key factor in the effectiveness of radiation therapy. Although the basic geometric arrangements used for placement of radiation sources in the uterus and vagina have not changed greatly since the 1930s, the development of remote afterloading techniques, image guidance and other technological advances have resulted in marked improvements in our ability to optimize brachytherapy dose to tumor and critical structures. However, the huge volume of locally advanced cervical cancer cases in medically underserved countries and the rarity in more developed countries pose particular challenges to the radiation oncologists who treat these cases. Factors that should be considered in the selection of brachytherapy applicators, methods, doses, and integration with external chemoradiotherapy will be discussed.


Vaginal Cancer

Patricia J. Eifel


The radiation oncologist plays a central role in the treatment of most invasive vaginal cancers because definitive surgical resection usually cannot be achieved without loss of normal bowel or bladder function. However, primary vaginal cancers pose particularly difficult challenges for radiation oncologists because they are very rare, because highly specialized techniques are required to achieve the best outcomes, and because the proximity of critical structures causes the window for complication-free cure to be narrow. Widely differing techniques may be used depending on the initial location, and distribution of disease and on the response to initial external beam irradiation. In most cases, intracavitary or interstitial brachytherapy provides an ideal way of maximizing the ratio between the doses to tumor vs. normal tissues. However, highly conformal external beam techniques are also extremely useful in selected cases. Some of the factors that drive treatment selection will be discussed. Fortunately, with careful, skilled management most patients with primary vaginal cancer can be cured of their disease.


Comprehensive quality management for clinical brachytherapy

Mark Rivard
Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts, United States of America

To facilitate the safe use and accurate delivery of brachytherapy, a Quality Management Program (QMP) should be devised to establish good clinical practice. A QMP mission could be that, “patients will be treated safely, accurately, and efficiently as defined by the prescription, regulations, and societal standards.” The QMP will incorporate departmental-specific issues like workflow, workload, and available resources. Elements of the QMP include training (initial and ongoing) of staff, preparation of policies and procedures, and establishment of quality controls, quality indicators, and quality assurances tests. Approaches to risk assessments may be top-down (e.g., fault-tree analysis) or bottom-up (e.g., failure mode, effects, and criticality analysis). The scope of QMP ranges from pre-purchase preparations and installation, acceptance testing of the equipment upon manufacturer delivery, commissioning of a clinical brachytherapy program, and the necessary on-going processes to ensure the safe use and accurate delivery of brachytherapy. The presentation will cover example errors in clinical brachytherapy with analyses performed to understand why the errors occurred and how to prevent them in the future.


Brachytherapy dose calculations and source strength determination

Mark Rivard
Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts, United States of America

Worldwide, brachytherapy dose calculations are based on the Task Group 43 (TG-43) dosimetry protocol by the American Association of Physicists in Medicine (AAPM). This formulism uses common equations across all treatment planning system (TPS) platforms to permit consistent derivation of brachytherapy dose. The equations permit accounting for source orientation when indicated with medical imaging (i.e., the 2D formulism) or when the locations of sources are known but their orientations are not (i.e., the 1D formulism). Components to TG-43 formulism include the brachytherapy source strength, dose-rate constant, geometry function, radial dose function, and either the 1D or 2D anisotropy function. The presentation will describe these dosimetry parameters and explain how they come together towards permitting brachytherapy dose calculations. Tips will be given on how to perform acceptance testing for a brachytherapy source already present in a clinical TPS. An important aspect of the TG-43 formulism is to measure the source strength of a particular brachytherapy source preceding clinical use. Measurement techniques and associated uncertainties will be covered, indicating best practice-standards according to recommendations by the AAPM and the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO).


Advances in brachytherapy dose calculation algorithms: State-of-the-art and developments underway

Mark Rivard
Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts, United States of America

With the recent introduction of heterogeneity-correction algorithms for brachytherapy, the community is still unclear on how to commission and implement these into clinical practice. The recently-published Task Group 186 (TG-186) provided guidance to early adopters of model-based dose calculation algorithms (MBDCAs) for brachytherapy dose calculations to ensure practice uniformity. This report represented recommendations by the American Association of Physicists in Medicine (AAPM), the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO), the American Brachytherapy Society (ABS), and the Australasian Brachytherapy Group (ABG). Extending this project, a working group has been formed by the AAPM/GEC-ESTRO/ABG to develop a set of well-defined test case plans to benchmark brachytherapy treatment planning systems using MBDCAs to support their commissioning by clinical end-users. To date, four test case plans have been developed for two high-dose-rate 192Ir treatment planning systems with work underway to develop clinical test cases and explore low-energy electronic brachytherapy sources and planning systems. Further, the test cases and a User’s Guide have been posted on the Brachytherapy Source Registry maintained by the AAPM and the IROC Houston QA Center. This Registry is available worldwide and provides access to a users’ forum for sharing experience and giving recent information and updates.


Research advances in brachytherapy physics: A perspective on technological advancements

Mark Rivard
Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts, United States of America

While brachytherapy has been applied for over a century, there continue to be substantial advances in delivery techniques and medical devices. These include applying the radiation dose more accurately, more uniformly irradiating the target, delivering higher doses to the target and lower doses to healthy structures, or enhancing patient convenience such as quicker or out-patient treatments. Novel applicators, needle tracking technologies, and in vivo dosimetry methods are being investigated. New radionuclides being considered for brachytherapy include 57Co, 75Se, 101Rh, 144Ce, 153Gd, 169Yb, and 170Tm. These are considered due to their half-lives, radiation range, specific activity, and manufacturing feasibility. Other novel brachytherapy sources contain multiple radionuclides, sources with directional emissions to preferentially irradiate the target, sources that elute chemotherapy agents, or sources with dissolvable encapsulation. Electronic brachytherapy sources are becoming more widespread, and are being better integrated into the existing infrastructure of source calibrations, dose calculations, patient imaging, and treatment delivery. Examples will be presented to highlight the attributes and current hurdles for innovative brachytherapy sources and devices.


Brachytherapy Education

Gerard Morton


Although brachytherapy is the most conformal method of radiation treatment delivery and has been shown to produce best cancer control outcomes in many disease sites, its use has been in decline in many parts of the world. While financial and logistic considerations may be partly responsible for this decline, failure to train the next generation in brachytherapy techniques has been identified as a significant factor. In Canada, radiation oncology residency training is being transitioned to Competence by Design, where specific competencies including those around brachytherapy need to be taught by the programs and achieved by the residents. The Royal College of Physicians and Surgeons of Canada have also developed an Area of Focused Competence Diploma in Brachytherapy, which can be awarded to physicians successfully completing an accredited brachytherapy training fellowship, or to those in practice through a different route. Specific competency Milestones need to be achieved. Our expectation is that these initiatives will standardize brachytherapy training, improve quality of treatment delivery and further facilitate clinical use of brachytherapy.


Salvage brachytherapy following external beam failures

Gerard Morton


Local recurrence following external beam radiotherapy occurs in 10-40% of cases. Expectant management with androgen deprivation is often appropriate, but for some, particularly younger men with higher grade disease, local salvage is appropriate. Salvage prostatectomy has a success rate of 50-80%, but is associated with a Grade 3 or 4 toxicity rate of up to 33%, particularly bladder neck contracture and incontinence. Either LDR (as per RTOG 0526) or HDR brachytherapy can be used as salvage options with a similar range of cancer control rates for whole gland treatment, but with a range of Grade 3 or 4 toxicities of between 0 and 47%. Local recurrence is often first at the site of initial bulk disease, suggesting a role for focal or focal boost brachytherapy treatments. Multiparametric MRI is used to identify location of recurrence, and this may be targeted using co-registration during HDR planning. Our initial experience using 13.5 Gy x 2 to the focal lesion reveals excellent tolerance without grade 3 toxicity, but with recurrence elsewhere within the prostate in over 20%. Our current protocol delivers 13.5 Gy x 2 to the target lesion, but treats the remaining prostate to 10.5 Gy with each fraction. It is well tolerated acutely and efficacy data is awaited.


Management of high risk prostate cancer

Gerard Morton


ASCO guidelines recommend that brachytherapy boost, either with LDR or HDR, should be offered to eligible patients with intermediate and high risk prostate cancer. This is based on results of three randomized clinical trials, all showing improved cancer control rates with the addition of brachytherapy. The Canadian multicenter ASCENDE-RT clinical trial randomized men with unfavourable risk localized prostate cancer to either 32 Gy external beam radiotherapy or an iodine-125 implant of 115 Gy, following pelvic radiotherapy to a dose of 46 Gy. All received a total of 12 months androgen deprivation therapy. Brachytherapy boost was associated with a 54% reduction in risk of biochemical failure, an absolute difference of over 20% at 9 years (17% vs. 38%). There was more toxicity in the brachytherapy arm with a cumulative incidence of grade 3 urinary toxicity of 19% vs. 5%, and 5-year prevalence of 9% vs. 2%. It is likely that the high urethral stricture rate was partly related to implant technique and can be reduced by limiting dose to membranous urethra or by use of HDR. Unanswered questions include the optimal duration of androgen deprivation therapy, role of pelvic radiotherapy, and need for other systemic options.


HDR Monotherapy for prostate with extreme hypofractionation

Gerard Morton


Low dose-rate (LDR) brachytherapy has emerged as a preferred treatment option for many men with low and intermediate risk prostate cancer. High dose-rate (HDR) brachytherapy has potential advantages including less short-term toxicity and more consistent dosimetry. Mature data using 3, 4 or 6 fractions reports equally good long-term cancer control rates with little toxicity. Delivering multiple fractions, however, is logistically challenging, inconvenient for patients, costly, and resource intensive. In recent years there has been interest in exploring more hypofractioned HDR monotherapy regimens involving two or single fractions, taking advantage of prostate cancer’s low alpha/beta ratio. We have completed a randomized clinical trial of HDR monotherapy delivered as either a single fraction of 19 Gy, or as two fractions of 13.5 Gy delivered one week apart. We have found both regimens to be very well tolerated, with less urinary and sexual toxicity in the single fraction arm during the first 12 months. It remains uncertain if single 19 Gy provides sufficiently high cancer control rates, and current direction is to further escalate the single fraction dose using intra-prostatic boosting. An ongoing Canadian randomized trial is comparing single fraction HDR with a standard iodine-125 LDR implant.


Electronic brachytherapy: commissioning and clinical experience of the Esteya® system for superficial treatments

Bess Sutherland
Radiation Oncology Centres
Medical Physicist

Guy Godwin
Director of Physics, ROC QLD
Radiation Oncology Centres

Danielle Tyrrell
Site Senior Medical Physicist
Radiation Oncology Centres

Background and Purpose

Electronic brachytherapy involves the use of a high dose rate (HDR) x-ray source placed close to, or in contact with, an area requiring radiation therapy treatment. The benefits of electronic brachytherapy include the low energy and high dose rate, resulting in minimal room shielding requirements and treatment times in the order of 2-3 minutes. The sharp penumbra, accurate source positioning, and steep fall-off makes brachytherapy suitable for superficial lesions. Additionally, electronic brachytherapy can be used without the additional radiation safety considerations associated with brachytherapy radioisotopes.

The Esteya® (Elekta Brachytherapy, Veenendaal, The Netherlands) operates at a single tube voltage of 69.5 kVp. The system selects one of three available dose rates to keep treatment times to approximately 2 minutes. Circular applicators of 10 mm – 30 mm diameter are available for treatment.

This work presents the commissioning and clinical use of the first Esteya® unit in Australia.

Methods

The Esteya® system was commissioned following recommendations from Candela-Juan et al. Tests included output reproducibility, dose linearity, half-value layer (HVL) determination, percentage depth dose (PDD), effective source to surface distance (SSD), and applicator factor measurements. The flatness, symmetry, and penumbra for each applicator was measured with EBT3 film. Absolute dosimetry was performed in-air following the American Association of Physicists in Medicine (AAPM) Task Group 61 (TG-61) recommendations. The Esteya® QA check device sensitivity was also tested using foils to simulate output variation.

Results

Results from commissioning are presented. The Esteya® unit was found to have reproducible output and the dose was seen to be linear with time for all three dose rates. The unit was found to have a sharp penumbra < 1 mm for all applicators. Applicator factors were compared to the Esteya® internal applicator factors as well as to published data.

Absolute dosimetry was performed following the AAPM TG-61 protocol using an ARPANSA calibrated PTW 23342 0.02cc soft x-ray chamber in-air. The HVL was determined to be 1.7 mm Al and the dose rate for all three mA settings was found to be within 2% of the tube certificate.

Conclusions

The Esteya® system has been commissioned for clinical use for superficial lesions.

References

Candela-Juan C et al. Commissioning and periodic tests of the Esteya® electronic brachytherapy system, J Contemp Brachytherapy 2015; 7, 2:189-195

Ma CM et al. AAPM protocol for 40-300 kV X-ray beam dosimetry in radiotherapy and radiobiology, Med Phys 2001; 28: 868-893


Feature Finding for Catheter Localization in HDR Prostate Brachytherapy

Kyle Ewert
School of Applied Sciences, RMIT University, Melbourne, VIC, Australia
MSc Student

Kyle Ewert
MSc Student
School of Applied Sciences, RMIT University, Melbourne, VIC, Australia

Ryan L Smith
Radiation Oncology Medical Physicist
School of Applied Sciences, RMIT University, Melbourne, VIC, Australia; Alfred Health Radiation Oncology, Alfred Health, Melbourne, VIC, Australia

Max Hanlon
PhD Student
School of Applied Sciences, RMIT University, Melbourne, VIC, Australia

Rick Franich
Lecturer / Program Co-ordinator
School of Applied Sciences, RMIT University, Melbourne, VIC, Australia

Background

Due to the high doses involved in HDR Brachytherapy, incorrect delivery can result in imperfect treatment to the patient. Causes of incorrect treatment delivery can include catheter displacements due to tissue swelling. An approach that mitigates the risk of possible mis-deliveries is that of pre-treatment catheter localization using x-ray imaging and radio-opaque markers, to delineate the course of the catheters, allowing comparison with planned positions [1].

Purpose

Currently in the clinic, an A-P pre-treatment image is acquired using a flat panel detector (FPD) and the paths of catheter markers are manually marked for comparison with the TPS. This is a time-consuming process and potentially introduces inaccuracies. The aim of this investigation was to establish an automatic approach to locating the catheter markers and characterizing the displacement relative to the planned positions.

Methods

Pre-treatment images were acquired using overhead x-ray and FPD, of a solid water phantom containing fiducial markers and radio-opaque markers inserted into selected catheters. MATLAB code was used to perform contrast-limited-adaptive-histogram-equalization (CLAHE) to enhance feature-finding in a defined region of interest encompassing the implant. Initial `guess’ positions of the fiducial markers and small linear segments of markers were used to initiate the program, which then employs a region-growing process to accurately locate their positions and extent. The determined positions allow the program to automatically extrapolate to the next, unselected marker position. This iterative process determines the next marker locations using the prior marker positions and angles to predict the next position. When complete, the program returns the identified catheter channel number.

Results

Six sets of images were analysed: four phantom and two patient images. The process identified catheter paths as illustrated in figure 1. The extrapolation routine handled simple instances of catheter marker overlap and moderate curvature. A mean marker detection rate of 79% for the phantom images with no overlap, 72% with overlap and 29.5% for the patient images was achieved. Channel number identification was more difficult, with varying rates of success: 59% for the phantom images with no overlap, 30% with overlap, and is yet to be implemented for patient images.

Conclusions

This program demonstrates a method for automatically delineating radio-opaque catheter marker locations in the pre-treatment workspace, allowing for a reduced clinician time overhead. With the markers located, this potentially allows for automatic image registration and offset characterization, resulting in an easily obtained metric for determining the divergence of implant geometry from the plan.


Towards Augmented Reality: Intraoperative Prostate Modelling for Biopsy and Brachytherapy

Mohammad Ali Jan Ghasab
Monash University
Student

Andrew Paplinski
Associate Professor
Faculty of Information Technology, Monash University

John Betts
Senior Lecturer
Faculty of Information Technology, Monash University

Hayley Reynolds
Research Fellow
Peter MacCallum Cancer Centre

Annette Haworth
Professor of Medical Physics
School of Physics, The University of Sydney

Background and Purpose:

Visualization of the prostate is being used increasingly to improve the accuracy of biopsies and seed placement during brachytherapy. One approach is to create a 3D model of the patient’s prostate from a stack of MR images pre-operatively and to fuse this inter-operatively with real time TRUS imaging.

The current practice of manually segmenting the 2D MR images pre-operatively and manual co-registration with TRUS images inter-operatively requires a very high level of expertise and is time-consuming.

In order to improve on current practice, we propose to create an augmented reality 3D prostate model automatically from the pre-operative MR images and real time TRUS, suitable for a clinician to use inter-operatively.

To achieve this, we improve upon the current state of the art in prostate boundary detection and 3D model creation for MR and TRUS imaging, and introduce fast optimisation models for the deformable registration of the 3D prostate models created in each modality.

Methods:

Beginning with the patient’s pre-operative 2D MR images we create a 3D voxel-based image stack from which a 3D model describing the patient’s prostate surface and interior is created directly by fitting a 3D Active Appearance Model (AAM) [1] using a Modified Inverse Compositional Model Alignment (ICMA) approach. This forms the MR reference model. TRUS images, made intra-operatively, are then used to update the 3D reference model in real time. This enables the detailed MR image data to be fused with real-time TRUS image in any plane. In this way we create a realistic 3D deformable prostate model, which can provide full volumetric and surface information to surgeons inter-operatively.

Results and Conclusion:

We have addressed two necessary steps in achieving the augmented reality model outlined above in the following ways: We have compared our 3D segmentation method with the best results presented in the MICCAI competition [2] and achieved better 3D segmentation accuracy with reduced computational time. Our results also show that the ICMA approach also produces segmentation results for TRUS slices to a high degree of accuracy and computational efficiency.

References:

[1] Mitchell, Steven C et al. “3-D active appearance models: segmentation of cardiac MR and ultrasound images,” in IEEE Transactions on Medical Imaging, vol. 21, no. 9, pp. 1167-1178, Sept. 2002.

[2] Litjens, Geert et al. “Evaluation of Prostate Segmentation Algorithms for MRI: The PROMISE12 Challenge.” Medical image analysis 18.2 (2014): 359–373. PMC. Web. 14 Nov. 2016.


Interstitial HDR brachytherapy for an infant with prostate and bladder rhabdomyosarcoma

Emily Flower
Crown Princess Mary Cancer Centre; Institute of Medical Physics, University of Sydney
Senior Radiation Oncology Medical Physicist

Kathy Tran
Radiation Therapist
Crown Princess Mary Cancer Centre

Salman Zanjani
Radiation Therapist
Crown Princess Mary Cancer Centre

Alicja Wach
Radiation Oncology Medical Physicist
Crown Princess Mary Cancer Centre

Wayne Smith
Radiation Therapist
Crown Princess Mary Cancer Centre

Jonathan Karpelowsky
Surgical Oncologist
The Childrens Hospital at Westmead

Angus Alexander
Paediatric Urologist
The Childrens Hospital at Westmead

Joseph Bucci
Radiation Oncologist
St George Hospital

Jennifer Chard
Radiation Onoclogist
Crown Princess Mary Cancer Centre

Background and Purpose: An 11 month old infant was treated with high dose rate brachytherapy alone for tumour management, following chemotherapy for a prostate/bladder embryonal rhabdomyosarcoma.

Methods:Pre-plans were completed on post chemotherapy imaging to ensure a brachytherapy approach was appropriate. Cystoscopy at the time of implant confirmed no macroscopic disease in the bladder itself and a small volume disease in the bladder neck. A combination trans-perineal and and trans-abdominal interstitial implant was achieved with trans-rectal ultrasound guidance and a direct surgical view. The ureters were transposed and reimplanted to avoid the high dose region. Daily CT imaging was used to confirm that the needle placement was correct.

Results: High dose rate brachytherapy was used to deliver a dose of 32.5 Gy to D98, with an EQD2 of 45 Gy. Organs at risk, including the rectum, bones, urethra, ureters and uninvolved bladder received acceptable doses.

Conclusions: A safe delivery of a fractionated, peri-operative high dose rate brachytherapy was achieved, with acceptable dosimetry dosimetry to both the clinical target volume and organs at risk. This involved co-operation across three different hospitals and a multi-disciplinary team.


Clinical Outcome of CT guided adaptive HDR brachytherapy combined with IMRT with chemotherapy in patients with locally advanced cervical cancer- The Royal Adelaide Hospital Experience

Kasri Abdul Rahim
Department of Radiation Oncology, Royal Adelaide Hospital
Clinical research fellow

Raghu Gowda
Radiation Oncologist
Royal Adelaide Hospital

Scott Carruthers
Radiation Oncologist
Royal Adelaide Hospital

Braden Higgs
Radiation Oncologist
Royal Adelaide Hospital

Wendy Phillips
Radiation Oncology Medical Physicist
Royal Adelaide Hospital

Angelo Katsilis
Senior Radiation Therapist
Royal Adelaide Hospital

Purpose:

To analyse early clinical outcomes with CT based imaged guided adaptive HDR brachytherapy combined with EBRT+chemotherapy for locally advanced cancer of cervix.

Materials and Methods:

Between June 2013 and Aug 2016, 52 consecutive patients with locally advanced cancer of cervix were treated with EBRT (45Gy/25F) +chemotherapy using IMRT followed by 3 fractions of 8-8.5Gy HDR brachytherapy over 3 weeks with HR CTV concept (EMBRACE trial). CT based planning and US confirmation was used for 1st fraction and US based confirmation only for 2nd and 3rd fractions. Dose volume adaptation was performed with the aim of dose escalation in large tumours ( D90 >85Gy). Interstitial needles were used as per clinicians’ discretion. Dose volume constraints ( D2cc) were <75Gy for rectum and sigmoid and <95Gy for bladder.

Patients were prospectively followed up for efficacy (Imaging PET or clinical assessment) and Grade 3/4 toxicity mainly (modified RTOG – bowel/bladder toxicity scores).

Results

52 patients ( median age 51.9 years) with cervix cancer FIGO IB- IVA were treated with definitive intent. Histology was Squamous Cell Carcinoma in 44 ( 85 %) , tumours size was > 5cm in 22 (43 %), LN involvement 24(46%).

Median follow up was 20.9 months (minimum 3months). Mean OTT was 55.1 days (range 38-76). 73% completed 4 cycles of chemotherapy.

19 % patients developed Grade 3 neutropenia and one patient (2%) had a grade 4 neutropenia.

Interstitial needles were used in addition to intracavitary brachytherapy in 24 (46 %). Total prescribed mean dose (D90) was a 90.14 Gy, D2cc bladder 87.5 Gy,D2cc Rectum= 64.46Gy and D2cc Sigmoid= 76.35Gy.

PET was done in 44% . Overall LC was 94 (%)

79% are disease free. 21% had relapsed – majority were distant (outside radiation field- sites)

There were total of 4 cases with Grade III/IV toxicity (GI/GU) – Entero- enteric fistula requiring stoma. Grade 3 GU toxicity ( haemorrhagic cystitis)was seen in two patient (4%), and radiation induced necrosis of vagina in another patient (2%). All three patients require HBO2.

Conclusions:

Early follow up data with IMRT and CT based image guided brachytherapy for locally advanced cervix cancer shows good local control and acceptable toxicity. Using interstitial needles is associated with superior D90 especially in those who still have bulky residual disease at the time of brachytherapy. DM is the main site of relapse


Clinical demonstration of the value of in vivo Brachytherapy Image-Guided Verification (BIGV) in high dose rate prostate brachytherapy

Hayley Mack
Alfred Health Radiation Oncology
Radiation Therapist

Vanessa Panettieri
Medical Physicist
Alfred Health Radiation Oncology

Annette Haworth
Professor
University of Sydney

Jeremy Millar
Radiation Oncologist
Alfred Health Radiation Oncology

Bronwyn Matheson
Radiation Oncologist
Alfred Health Radiation Oncology

Max Hanlon
PhD Candidate
RMIT University

Rick Franich
Professor
RMIT University

Ryan Smith
Medical Physicist
Alfred Health Radiation Oncology

Background & Purpose.

High dose-rate (HDR) brachytherapy treatment verification is important, but technically difficult. Errors would have significant clinical impact on the patient. Pre-treatment imaging can provide information to ensure the implanted catheters are in the correct position prior to dose delivery. In vivo source tracking during treatment provides further verification that the treatment is delivered to the patient as prescribed.

We report a clinical study of our experience with our novel Brachytherapy Image-Guided Verification (BIGV) flat panel detector (FPD) based system for HDR prostate brachytherapy.

Materials & Method.

A FPD was mounted in our treatment couch. The patient was positioned with the target region (prostate) centred over the imaging area. Radio-opaque markers were inserted into selected catheters and we acquired an AP image of the implant for comparison with the treatment planning system (TPS). Treatment commenced after the correct planned catheter positions were confirmed. During treatment patient exit radiation was acquired with FPD imaging. The exact dynamically-tracked position of the source inside the patient was determined with image-processing and was compared to the treatment plan.

Results.

Well defined pre-treatment imaging geometry allowed registration with the TPS and quantitative evaluation of potential catheter displacement. Source tracking during treatment provided a visual verification that treatment was proceeding as planned. Processing of the delivered source dwell positions verified correct treatment plan delivery. Delivered dose was reconstructed to compare with the planned TPS dose.

Conclusion.

Visual in vivo source tracking provided confidence the planned treatment was delivered as prescribed and processing confirmed the treatment was delivered free of potential human related errors. The present and future of this system improves safety standards by allowing routine treatment verification in HDR brachytherapy across a range of clinical applications.


Interactive biologically-based inverse planning for focal LDR brachytherapy of prostate cancer

JIE LIU
Monash University
PhD student

Tim Dwyer
A/Prof
Monash University

Kim Marriott
Prof
Monash University

Jeremy Millar
A/Prof
The Alfred Hospital

Annette Haworth
Prof
The University of Sydney

Background and Purpose

As an alternative to the whole gland treatments, focal therapy aims to destroy the tumour cells while minimising damage to surrendering healthy tissues and structures. A biologically based model — tumour control probability (TCP) is used to relatively measure the quality of a focal plan. There is no general way of how biologically-based focal planning should be done. Using inverse planning techniques to create focal plans with appropriately applied objectives and constraints is promising. But this technique is not widely used in seed brachytherapy at the moment. Introducing interaction into the inverse planning technique to provide clinicians with greater controls over the optimisation process is proposed.

Methods

Achieving theoretically high rates of tumour control while maintaining low dose of radiation to both the urethra and rectum is possible with an inverse planning technique using a focal LDR brachytherapy approach [1]. In this study, we focus on using interactive inverse planning technique to answer the following questions:

(1).What should a clinically sound focal plan look like?

(2).What kind of user interactions and visualisations are required to facilitate clinicians in creating and evaluating biologically-based focal plans for prostate cancer?

Results

An interactive web interface has been developed. it can produce focal treatment plans using different optimisation search strategies. It also provides users with interactive controls over the optimisation process, such as pausing the optimisation and adjust needle positions, locking existing needles and re-optimise. Produced treatment plans can be compared in real time to facilitate selecting the preferred treatment plan. Currently, a two-stage semi-conducted interview with the clinical community is undergoing. Future developments will provide greater control and improved display tools according to the feedback from the conducted interviews.

Conclusions

The optimal approach to focal brachytherapy planning is yet to be established. Even though focal treatment plans can be produced using inverse planning in a short period of time, using interactive inverse planning to produce better and more personalised focal treatment plans is the next step. However discussions and experiments are required to clarify how to help clinicians to better understand how to produce focal plans and also how to use interactive inverse planning effectively to support users in using experience and knowledge for focal plan creation and evaluation.

References

[1].Haworth, Annette, et al. "A radiobiology-based inverse treatment planning method for optimisation of permanent l-125 prostate implants in focal brachytherapy." Physics in medicine and biology 61.1 (2015): 430.


Re-implantation of Iodine-125 seeds for suboptimal prostate brachytherapy post-implant dosimetry: clinical and dosimetric outcomes

Andrej Bece
St George Hospital
Radiation Oncology Fellow

Komiti Enari
Medical Physicist
St George Hospital

Andrew Howie
Medical Physicist
St George Hospital

Yaw Chin
Radiation Oncologist
St George Hospital

Joseph Bucci
Radiation Oncologist
St George Hospital

Background:

Dose parameters on post-implant dosimetry (PID), particularly prostate D90, have been correlated with biochemical disease outcome following permanent prostate brachytherapy (PPB)1. As such, routine PID is recommended by international consensus guidelines2. In cases of suboptimal dosimetry both supplemental external beam radiation (EBRT) and permanent seed re-implantation (RI) have been utilised. To date there are only limited case series describing RI for suboptimal PID. We aim to report our technical and clinical experience with RI in this subset of patients.

Methods:

1,116 patients underwent PPB using Iodine-125 seeds between February 2002 and November 2016. Post-implant dosimetry with US-CT fusion was performed at day 30. All patients were followed up at 4-12 month intervals for biochemical or clinical recurrence. Toxicity and quality of life (QOL) was assessed prospectively using validated tools (IPSS, IIEF, QLQ C30, EPIC Bowel). Patients were offered RI where PID was poor (D90 < 119 Gy or V100 < 75%) or suboptimal (D90 < 130 Gy or V100 < 85%) and where dose deficiency correlated with known disease on biopsy. An analysis of all patients undergoing RI was undertaken, reviewing dosimetric, biochemical, clinical and toxicity outcomes.

Results:

8 patients were identified who underwent RI since March 2011. 543 patients over this same period had a single PPB implant. Day 30 post-implant median D90 and V100 were 126 Gy (82.5-135.0 Gy) and 78.0% (47.5-84.74%), respectively. 7-24 (mean 13) additional seeds were re-implanted at a median 63 days (42-252 days) after initial implant. Biopsy-proven disease was present at the site of under-dosing in all patients. Re-implantation dosimetry was excellent in all patients with median cumulative D90 and V100 of 157 Gy (140-175 Gy) and 93.9% (86.2-98.0%), respectively. Median follow up for patients treated prior to 2016 (n=5) was 22 months. There were no biochemical or clinical recurrences and toxicity and QOL outcomes were comparable to contemporaneous patients undergoing a single implant. No grade 3 adverse events occurred in these patients. One patient developed a benign PSA bounce.

Conclusions:

We present the largest series of PPB re-implantation for patients with initially suboptimal dosimetry. RI improves subsequent PID while avoiding the need for supplemental EBRT. There were no biochemical or clinical failures in these patients and no increase in toxicity over that expected from primary PPB. Judicious use of RI should be considered a standard approach in experienced centres where PID is inadequate.


MaxiCalc: a real-time dose calculation engine for use in a HDR brachytherapy source tracking system

Max Hanlon
RMIT University
PhD Candidate

Ryan Smith
Senior Medical Physicist
Alfred Health Radiation Oncology

Rick Franich
Professor of Medical Physics
RMIT University

Background and Purpose

An aspect of treatment verification in HDR brachytherapy involves calculating the dose from the measured source dwell positions. Current TPSs cannot reconstruct delivered dose measured by our source tracking verification system, as they can only utilise dwell positions that reside within previously defined catheter paths. Due to this, a fast dose calculation engine (DCE) that can accept the input of arbitrary dwell positions from the source tracking system is required. Here we present a TG-43 based DCE that computes 3D dose grids for measured dwell positions and allow comparison with the treatment plan.

Methods

The DCE, dubbed MaxiCalc, calculates dose grids using the input of measured dwell positions and times, allowing direct comparison to the treatment plan. MaxiCalc was validated against Oncentra Brachy (OCB v4.3) at 27 single dose points, as per OCB commissioning, as well as a 3D dose grid of 13 dwells.

Dwell positions and times delivered in a phantom were measured by our source tracking system, as previously published.[1] The measured dwell positions were then used as input to MaxiCalc and the resultant dose grid compared to that from OCB. Observed dose differences due to source position measurement uncertainties were investigated.

Results

For the 27 dose points, MaxiCalc differed from OCB by a mean of 0.08% (σ=0.07%, max 0.41%) demonstrating differences that are similar to those between published values [2] and OCB. In a multi-source plan for doses between 50-200% of the prescription dose, MaxiCalc has a mean agreement of 0.2% with 98% of points agree by <1%. For doses above 50% of the prescription, the 3D gamma pass rate (1%/1mm) is >99%.

A dose grid was generated from the measured positions from a delivered plan of 25 dwells, with a mean deviation between planned and measured positions of 0.6 mm. Comparing to the planned dose, the dose difference due to difference in measured positions can be clearly seen in figure 1. Results from measured delivery errors such as these will also be presented.

Conclusion

MaxiCalc provides a tool to perform real-time dosimetric treatment verification in conjunction with our source tracking system. It can overcome limitations of clinical TPSs by providing fast dose calculations for arbitrary measured dwell positions.

References

1. Smith, R L., et al. Medical physics 43.5 (2016): 2435-2442.

2. Daskalov, G M., Löffler E, and Williamson J. Medical physics 25.11 (1998): 2200-2208.


Improved prostate cancer survival with the addition of high dose-rate brachytherapy to external beam radiation treatment and low toxicity with 12-year follow-up

Jeremy Millar
Alfred Health Radiation Oncology
Director

Aaron Kent
Senior Registrar
Alfred Health Radiation Oncology

Bronwyn Matheson
Radiation Oncologist
Alfred Health Radiation Oncology

Ryan Smith
Radiation Oncology Medical Physicist
Alfred Health Radiation Oncology

Cath Beaufort
Head Radiation Therapist
Gippsland / Alfred Health Radiation Oncology

Daniel Zwahlen
Radiation Oncologist
Kantonsspital Graubunden, Chur, Switzerland

Ben Hindson
Radiation Oncologist
Christchurch Hospital, Christchurch, New Zealand

Peter Royce
Director
Urology, Alfred Health

Background and Purpose: Either low dose-rate (LDR) or high dose-rate (HDR) brachytherapy added to external beam radiation treatment (EBRT) for prostate cancer (PCa) has shown better disease-control in retrospective and randomised studies, but typically not in survival; and not usually with long-term adverse-effect (AE) descriptions. We report long-term follow-up with patient-reported quality-of-life (QoL) measures in a cohort of men with PCa treated with EBRT with or without an HDR "boost".

Materials and Methods: Consecutive men presenting 1998-2004 with localised PCa treated using departmental protocols including the clinician- and patient-choice optional addition of HDR boost to EBRT (HDR-EBRT) or EBRT alone (EBRT). NCCN intermediate risk (IR) men were offered neoadjuvant androgen deprivation (AD) and those with high risk (HR) were also offered adjuvant AD. Patient-completed QoL surveys were recorded at least annually to assign RTOG grades to bowel and bladder AE, and the 5-item international index of erectile function (IIEF-5) to assess erectile function (EF). Strictures were defined as time-to-first-urethrotomy. The Phoenix consensus defined biochemical failure (BF). EF was a IIEF-5 score>7. Times-to-event were assessed with Kaplan-Meyer methods.

Results: 654 patients received either HDR-EBRT (median 46Gy in combination with a HDR median 18Gy/3 boost; 215 patients) or EBRT (median 70Gy; 440 patients).The median age was 69yrs and 72yrs, and median presenting PSA 12.2ng/mL and 9.9ng/mL, for HDR-EBRT and EBRT groups respectively. The HDR-EBRT group had less low risk patients (3.3% vs 19.4%) and more HR (50.7% versus 37.4%) compared to the EBRT group. The 15-year estimates of BF-free survivals were 0.68 and 0.54 (P=0.03) for the HDR-EBRT and EBRT men respectively and the 15-year estimates for cause-specific and overall survivals were 0.87 and 0.79 (P=0.036), and 0.67 and 0.52 (P=0.0008). In HDR-EBRT men bowel and bladder AE prevalence peaked at 3-6 months, and the point prevalence of RTOG grade >1 bowel AE was never >5% after 7 years. The estimated probability of stricture was 11% at 15 years. Of men with documented EF pre-treatment, 42% had EF at 10 years.

Conclusions: In our cohort HDR-EBRT was associated with better disease control and survival than EBRT (noting EBRT dose was lower than current standards), despite these men having some features suggesting a poorer prognosis. Overall long-term AE prevalence was low, and EF was preserved in a proportion of men even 10 years after treatment. Our results add weight to observations from randomised trials and provide long-term statistics on AE associated with HDR-EBRT.


Characterisation of the Variseed Dynamic Volume Calculation Algorithm for Low Dose Rate Prostate Brachytherapy

Prabha Jones
Alfred Health - Gippsland Radiation Oncology
Radiation Oncology Medical Physics Registrar

Prabha Jones
Medical Physics Registrar
Gippsland Radiation Oncology, Alfred Health

Sarah Elliot
Senior Medical Physicist
Alfred Health Radiation Oncology, Alfred Health

Ryan L Smith
Senior Medical Physicist
Alfred Health Radiation Oncology, Alfred Health

Background: Low dose rate (LDR) prostate brachytherapy is a highly conformal internal radiation therapy that delivers a high dose of radiation to the prostate by permanently implanting I-125 seeds. Due to the close proximity of the urethra, bladder and rectum, it is important to ensure precise contouring of structures and the careful planning of source positions. Dose-Volume Histogram (DVH) indices are used to monitor dose to the target and organs at risk. Aim: Variseed treatment planning system (TPS) has introduced an updated version (V9) for which the volume calculation algorithm has changed to a dynamic grid approach, compared to a static grid in the previous version (V8). The aim of this work is to characterise the effects of the dynamic volume calculation on clinical LDR pre-plans for Variseed V9. Method: The pre-planned data of 40 consecutive patients treated between 2015 and 2016 were analysed. Each patient plan was re-calculated in V9 and structure volumes and selected DVH indices (D100%, V100%, V150%, V200%) for the target were compared with V8. This method was also applied to a CIRS multimodality pelvic phantom with known anatomical prostate volume. Results: For the 40 patients evaluated, the total calculated volume of the urethra, rectum and target were identical (within rounding) in both versions of Variseed. There was a 2% variation in the volume of the prostate between V8 (mean 36.74± 10.74 cm3) and V9 (mean 35.97± 10.74 cm3). Although the D100% and V100% for the target are similar in V8 and V9, the V150% and V200% were different and these results are clinically significant. In following our departmental pre-planning protocol, for 6 patients the V200% was below the minimum acceptable value of 13% in V9; for 17 patients the V150% was above the maximum acceptable value of 62% in V9. Further investigation on the prostate phantom showed the V150 % was also higher in V9. However, the V200% was higher in V9 for the prostate phantom which does not follow the trend observed in the patient data analysis. Conclusion: There are differences in the DVH statistics of identical prostate seed plans calculated in Variseed V8 and V9 due to the dynamic volume calculation algorithm introduced in V9. The magnitude of the differences observed in the V150% and V200% would lead to changes in source position and/or source numbers in the pre-planning stage of brachytherapy. To further understand the effects of the dynamic volume calculation algorithm on DVH statistics, the relationship between dose and the structure volume, structure shape, total number of sources and image slice spacing is being further investigated.


Assessing prostate tumour cell density for focal brachytherapy using multiparametric MRI and machine learning techniques

Yu Sun
The University of Melbourne
PhD student

Hayley Reynolds
Researcher
Peter MacCallum Cancer Centre

Darren Wraith
Lecturer
Queensland University of Technology

Scott Williams
Radiation oncologist
Peter MacCallum Cancer Centre

Catherine Mitchell
Pathologist
Peter MacCallum Cancer Centre

Annette Haworth
Professor
University of Sydney

Background and Purpose

In a specific form of focal brachytherapy validated by our group [1], termed ‘bio-focused’ therapy, reliable estimation is required for both tumour location and tumour biological characteristics which include cell density, aggressiveness and hypoxia. While previous studies have found a correlation between tumour cell density shown in histology data and apparent diffusion coefficient (ADC) values computed from multiparametric MRI (mpMRI), no quantitative predictive model has been reported for predicting tumour cell density using mpMRI data at a voxel level.

The aim of this study was to investigate the performance of machine learning methods to predict tumour cell density using mpMRI data. Following our previous work on tumour location prediction, we intended to apply similar methods, along with predictions of tumour aggressiveness and the presence of hypoxia, in bio-focused brachytherapy treatment, where non-uniform doses are calculated.

Methods

In vivo mpMRI data were collected from 29 patients before radical prostatectomy. Sequences included T2-weighted (T2w), diffusion-weighted (DWI) and dynamic contrast enhanced MRI (DCE-MRI). In vivo mpMRI was registered with histology (Reynolds, 2015), from which ground truth cell density was computed using an image processing pipeline involving colour deconvolution and non-maxima suppression.

Patients were partitioned into a training group and a test group. Haralick texture features were extracted from mpMRI data. Features with high correlations were excluded. The performances of two regression methods were assessed, including linear regression (LR) and multivariate adaptive regression splines (MARS). Parameter optimisation was performed within the training group using leave-one-out cross validation. The performance of final models was assessed by relative mean squared error (rMSE) on the test group. Paired t tests were performed for the statistical significance of different methods.

Results

Five features from mpMRI data and 17 Haralick texture features were selected. LR had an rMSE of 13.72 (±0.21) % and identified the most important mpMRI feature to a pharmacokinetic map from DCE-MRI, followed by ADC. MARS showed marginal improvement in rMSE (0.02%, p<0.01) over LR. Both methods gave consistent results for feature relative importance.

Conclusions

We developed a model for prostate tumour cell density prediction at a voxel level from mpMRI using regression methods and histology data for validation. Future work will investigate other non-linear regression methods and incorporate the prediction of tumour aggressiveness and hypoxia for biological optimisations in brachytherapy treatment planning.

References

[1] Haworth, A. et al. (2013). Validation of a radiobiological model for low-dose-rate prostate boost focal therapy treatment planning. Brachytherapy, 12(6), 628-636.

[2] Reynolds, H. et al. (2015). Development of a registration framework to validate MRI with histology for prostate focal therapy. Medical Physics, 42(12), 7078-7089.


The introduction and validation of a model based dose calculation algorithm for brachytherapy in an Australian centre.

Lynsey Hamlett
Townsville Hospital Cancer Centre
Advanced ROMP

Marcus Powers
Medical physicist
Townsville cancer centre

Michael Roche
Registrar
Townsville cancer centre

David Wood
Radiation Therapist
N/A

Louis Fourie
Director of Physics
Townsville Cancer Centre

Introduction

The Townville Hospital, QLD, is validating Elekta’s commercially available Advanced Collapsed Cone Engine (ACE©) these are the preliminary findings.

Method

Following AAPM report TG-186[1], reference plans were calculated using TG-43 for both level 1 and level 2 plan conditions.

For level 1 testing three plans; single dwell; two dwell; and an eight dwell circular arrangement were produced in a water equivalent cube phantom.

Level 2 testing used the test plans available from the AAPM/ESTRO/ABG working group registry (WGR) [2]. This introduced non water equivalent phantom materials. Finally complex ‘HDR prostate type’ CT plans using titanium catheters with 16 catheters and 205 dwell positions, 20 catheters and 205 dwells and 12 catheters and 137 dwells were investigated.

Each plan was recalculated using ACE© standard accuracy and ACE© high accuracy and compared to the TG-43 reference plans. Plans were compared both visually using the ‘Analyse’ module in Oncentra, using point doses and for the prostate type plans comparision via dose volume histogram (DVH).

Results

Level 1 results were similar to those published by Yunzhi Ma et al [3], dose differences were seen on the single dwell plan in regions of low dose positioned on the longitudinal axis i.e. passing through the source axis.

Level 2 plan results using the WGR data showed some small differences between the ACE© TG-186 calculations and the WDR data, these were visible on the dose wash comparison.

For the prostate plan using titanium catheters variation was visible(Figure 1) and enough to effect the plan quality i.e Urethra D10% reduced from 114.98% to 112.08% (DVH Figure 2).

The TG-186 accuracy modes showed negligible difference for the clinical plans, calculation times ranged from 10mins for standard to 120mins for high.

Conclusion

ACE© calculation algorithm produces dose distributions within water equivalent reference phantoms similar to TG-43. The results of the prostate plans suggest that titanium needles potentially introduce a variation in the dose distribution which could effect plan quality. Further work aims to investigate more clinical sites and to benchmark ACE© using Monte Carlo modelling.

References

[1] Beaulieu L et al(2012) Report of the Task Group 186 on model-based dose calculation methods in brachytherapy beyond the TG-43 formalism Med. Phys. 39 (10) 6208-36

[2] AAPM/ESTRO/ABG Brachytherapy Working Group

[3] Ma Y et al Validation of the Oncentra Brachy Advanced Collapsed Cone Engine for a commercial Ir192 source using heterogeneous geometries. Brachytherapy 14 (2015) 939-952


HDR and LDR Brachytherapy at the Royal Adelaide Hospital: A Statistical Review from 2004 to 2016

Wendy Phillips
RAH
Senior Medical Physicist

John Lawson
Acting Chief Physicist
RAH

Paul Reich
Acting Principal Physicist
Royal Adelaide Hospital

Purpose: This study provides an overview of the changes in brachytherapy services at the RAH over the past decade. Data on patient numbers, treatment techniques, treatment procedure times and staff requirements have been collected and presented to enable a review of the service development over this time-frame.

Methods: Data has been collected and analysed on a per annum basis for all of the HDR and LDR brachytherapy treatments that were delivered at the RAH from 2006 to 2016. This includes the commonly treated sites such as HDR prostate and HDR gynaecological to the less common treatments such as LDR eye plaques and HDR surface moulds. Statistics presented include patient numbers and treatment fraction numbers delivered, separated into treatment technique. Average staff number requirements, in terms of professional roles, and average treatment procedural times for each type of case are also discussed for the busy brachytherapy workload of this institution.

Results: Results will be presented in detail on the variety of treatments undertaken. In brief, patient referrals have continuously increased in number over the past 10 years, for example in 2006 HDR prostate cases numbered 11; while 2016 saw 77 patients treated. The HDR prostate service has also involved over the years from a 2 fraction boost treatment to either a single fraction boost, single fraction mono-therapy, or single fraction salvage therapy treatment. HDR vaginal cylinder treatments have been the most commonly treated technique, rising from 90 to over 230 treatment fractions delivered per year, over the 10 years studied. In this multidisciplinary clinical field, an experienced and dedicated team is vital, with current staff involvement ranging from 4 staff members for a simple HDR vaginal cylinder gynaecology case, to 9 staff members for a HDR intrauterine gynaecology treatment session.

Summary: The RAH brachytherapy program is extremely diverse and growing each year. It is currently the sole provider of HDR services for SA/NT and provides key treatment options as either a sole or combination radiotherapy treatment (boost) to external beam therapy. With the move to the new RAH in 2017, it is envisaged that the RAH brachytherapy program will continue to expand and develop while delivering this vital service to patients.

(Poster presentation)


In-vivo dosimetry: Methodology and results for HDR brachytherapy surface mould patients treated at the RAH since 2014

Paul Reich
Royal Adelaide Hospital
Acting Principal Physicist

Wendy Harriss-Phillips
Senior Medical Physicist
Royal Adelaide Hospital

John Lawson
Acting Chief Physicist
Royal Adelaide Hospital

Background and Purpose

In-vivo dosimetry is an important component to radiotherapy as it aims to verify that the prescribed dose is what is actually delivered to the patient .This is especially important in brachytherapy due to the reproducibility requirements associated with customised treatments (e.g. surface moulds) combined with steep dose gradients associated with the radioactive source. The aim of this work is to present our methodology and results for in-vivo dosimetry performed on surface mould HDR brachytherapy patients at the RAH since 2014.

Methods

In-vivo dosimetry is performed at the RAH using thermoluminescence dosimetry (TLD) or film dosimetry on our HDR surface mould patients as requested by our clinicians [1, 2]. Since 2014, 8 patients received HDR brachytherapy to sites ranging from the face and head to arm and leg extremities. In-vivo dosimetry was performed on 6 of these patients.

HDR brachytherapy is administered to our surface mould patients using a MicroSelectron ® remote afterloader equipped with an Ir-192 radioactive source. CT based treatment planning is performed with Oncentra® Brachy treatment planning system (using the AAPM TG 43 based dose algorithm). The TLDs or films are placed on the treatment area of the patient at day 1 of treatment. The position of the detectors is localised using anatomical landmarks on the patient (e.g. tattoos, scars). Depending on the vicinity of the treatment site to critical structures or organs (e.g. eyes), additional detectors are placed on these tissues as requested by the clinician. The dose measured from the irradiated detectors is compared to the dose calculated from the treatment planning system.

Results

On average (across 6 patients), the dose measured at the surface of the patient was within approximately ±10 % (range of ± 3 - 15 % ) of the dose prescribed to the patient. For all 6 patients, the dose measured at critical structures or organs were within clinically safe levels.

Conclusions

Our in-vivo dosimetry program for HDR surface mould brachytherapy at the RAH has provided us with valuable information and confidence on the dose delivered to our patients. Performing in-vivo dosimetry has also informed us on where improvements can be made in our methodology.

References

1. Radiation Oncology Practice Standards. A Tripartite Initiative. 2011.

2. Radiation Oncology Practice Standards. A Tripartite Initiative. Supplementary Guide. 2011.


APBI in patient with a defibrillator – a case study

Kristine Schreiber
St George Hospital Cancer Care Centre
Radiation Therapist

Breast Brachytherapy Team Poster presentation
brachytherapist
Cancer Care Centre St George Hospital

Mrs X a 66 yr old post-menopausal patient diagnosed with Lt sided breast cancer who was fitted with a defibrillator in 2014 was chosen for APBI as the defibrillator could not be resided to the other side and it was decided that APBI would be the best option for her treatment. The investigations before treatment were carried out using ultrasound and CT to determine if the seroma cavity was suitable for implant Defibrillator monitoring was carried out during the treatment with no adverse effect to the device or the patient Patient received 34gy in 10 treatments bi daily over 7 days Planning with APBI limited the dose to the defibrillator whereas a plan comparison with 6MeV gave full dose of 50Gy to the defibrillator There were a few challenges during implantation one was that the company had never faced this problem before and was used to megavoltage and not sure what brachytherapy was and also the uncertainty of where the leads were when implanting. Pt has had her 6 weeks follow up and skin was good and patient has had no problems


Round the bend – an unusual oesophageal brachytherapy case

Judith Martland
Northern Sydney Cancer Centre
Senior Physicist

Florence Ko
Radiation Therapist
Northern Sydney Cancer Centre

George Hruby
Radiation Oncologist
Northern Sydney Cancer Centre

Andrew Kneebone
Radiation Oncologist
Northern Sydney Cancer Centre

Background and Purpose

A 69 year old patient with oesophageal carcinoma presented for palliative radiotherapy, however due to very significant cerebral palsy resulting in severe scoliosis and contracture of limbs it was realised that stable immobilisation for external beam radiotherapy would be impossible. The patient was therefore considered for brachytherapy.

Methods

A dose prescription of 2400 cGy in 4 fractions over one week was prescribed, to a treatment distance of 1cm and a length of 5cm. A 5 french flexible catheter (Nucletron LumencathTM) with a marker wire in place was inserted into a nasogastric tube in-situ and passed beyond the tumour at the cardio-oesophageal junction. The patient was then CT imaged and a 3D reconstruction and patient plan produced. The brachytherapy treatment was delivered as planned, with the patient able to return to her care home shortly afterwards.

Results

The patient’s severely irregular anatomy and tortuous distal oesophagus made the planning process challenging, and reflux of gastric fluid through the nasogastric tube made catheter fixation difficult. The brachytherapy was nevertheless successfully delivered and at follow up seven months later the patient was well with no symptoms suggestive of recurrence and no evidence of radiation toxicity.

Conclusions

For this patient, brachytherapy provided an excellent treatment approach, enabling accurate 3D planning and treatment despite the patient’s pre-existing condition precluding immobilisation.


Verification of Skin Doses During Interstitial Brachytherapy APBI

Dean Cutajar
Centre for Medical Radiation Physics, University of Wollongong
Research Fellow

Taghreed Al-sudani
PhD Candidate
Centre for Medical Radiation Physics, University of Wollongong

Andrew Howie
Senior Physicist
St George Cancer Care Centre, St George Hospital, Kogarah

Andrej Bece
Postgraduate Fellow
St George Cancer Care Centre, St George Hospital / St George and Sutherland Clinical School, University of New South Wales

Anatoly Rosenfeld
Director/Research Leader
Centre for Medical Radiation Physics, University of Wollongong

Background and Purpose

Accelerated partial breast irradiation (APBI) involves radiotherapy treatment of the lumpectomy bed after breast conserving surgery. High dose rate (HDR) interstitial brachytherapy is a modality used to provide the treatment. With the advent of the AAPM Task Group 186 (TG186) recommendations, complex dose calculations improving the accuracy near interfaces (skin, cavities, applicators) are being adopted in a paradigm shift for brachytherapy dose planning, away from the traditional Task Group 43 (TG43) protocol1. This study investigated the effect of the skin-air interface on the skin dose during interstitial brachytherapy APBI by performing phantom measurements in comparison with TG43 based dose planning.

Methods

A gelatine-based breast phantom was constructed. Nine interstitial catheters were implanted into the phantom through a template and six surface locations were localised with markers to indicate points of interest. The phantom was scanned using CT, and Oncentra Brachy was used to reconstruct catheter paths through the treatment volume and to optimise the source dwell points, as well as generate dose metrics for the treatment. A plan was generated with a prescribed dose of 3.4Gy to a theoretical volume. MOSkin dosimeters were placed on the surface of the phantom at the points of interest. The treatment was delivered to the phantom three times, with the MOSkin doses recorded after each full treatment delivery.

Results

The MOSkin detectors all recorded doses below treatment planning system determined doses at the points of interest. The relative discrepancies ranged from 2% to 29%, with an average discrepancy of 15%. The largest absolute dose discrepancy being 30cGy below the calculated dose of 193cGy (15%), from a point of interest directly above the centre of the target.

Conclusions

The Dose planning in interstitial brachytherapy APBI using would benefit from the adoption of TG186 based dose planning. A lower than predicted dose to the skin may be beneficial to the patient, however, indicates there may be coverage issues for treatment volumes close to the surface. The MOSkin, a dosimeter designed to measure the dose to a patient’s skin during radiation therapy, was used, providing a pilot study for the development of an in-vivo quality assurance program for breast radiation therapy, involving brachytherapy or external beam deliveries.

References

1. Beaulieu. L, et al, “Report of the Task Group 186 on model-based dose calculation methods in

brachytherapy beyond the TG-43 formalism: current status and recommendations for clinical

implementation”, 2012, Med. Phys. 39 6208–36


HDR brachytherapy in vivo source tracking using a 2D diode array: A Monte Carlo study

Joel Poder
Centre of Medical Radiation Physics, University of Wollongong
Medical Physicist

Dean Cutajar
Research Fellow
Centre of Medical Radiation Physics, University of Wollongong

Susanna Guatelli
Senior Lecturer
Centre of Medical Radiation Physics, University of Wollongong

Marco Petasecca
Senior Lecturer
Centre of Medical Radiation Physics, University of Wollongong

Anatoly Rosenfeld
Director
Centre of Medical Radiation Physics, University of Wollongong

Background and Purpose: Due to uncertainties in catheter reconstruction during planning of high dose rate (HDR) brachytherapy treatments, as well as the potential for catheter shifts in the time between imaging and treatment, there exists a need for real-time source position verification to ensure safe and accurate treatment delivery. This study aims to assess the accuracy of source position verification using a 2D diode array [1] embedded below the patient in a carbon fibre couch. The effect of tissue inhomogeneities on the source triangulation accuracy is examined. Methods: Monte Carlo simulations of 12 source positions from a HDR prostate brachytherapy treatment were performed using the Geant4 platform [2]. An Ir-192 Flexisource (Isodose Control, Veenendaal, The Netherlands) was simulated inside a voxelised patient geometry, and the response of each detector in the couch embedded 11x11 diode array was evaluated. The detector response was then used to determine the distance of all detectors in the array to each of the 12 source positions. Finally, the source position was triangulated using an iterative procedure where the source position is first estimated, and then repeatedly refined based upon the agreement of the predicted geometric distance from the source to the detectors against those measured by the detectors in the array. Results: The accuracy of source position verification was found to be affected by the tissue inhomogeneities inherent in the patient geometry. As such, an inhomogeneity correction may be required, based on density information obtained from the patient CT scan performed prior to treatment. Furthermore, due to the relatively large distance between the source position and the diode array, it was found that source localisation accuracy can be improved with an increased number of detectors used in the triangulation algorithm. Conclusions: The effect of tissue inhomogeneities in the patient geometry on source localisation accuracy during a HDR prostate brachytherapy treatment was examined through Monte Carlo calculations. The localisation accuracy was found to be affected by the inhomogeneities; however this may be corrected for using density information obtained from CT. References: [1] Espinoza, A., B. Beeksma, M. Petasecca, et al., The feasibility study and characterization of a two-dimensional diode array in “magic phantom” for high dose rate brachytherapy quality assurance. Medical Physics, 2013. 40(11): p. 111702. [2] Archambault, L., L. Beaulieu, J.F. Carrier, et al. Overview of Geant4 applications in medical physics. in Nuclear Science Symposium Conference Record, 2003 IEEE. 2003.


BrachyView: Initial preclinical results for a real-time in-body HDR PBT source tracking system with simultaneous TRUS image fusion

Saree Alnaghy
Centre for Medical Radiation Physics, University of Wollongong
PhD Student

Mitra Safavi-Naeini
Research Associate ANSTO
Centre for Medical Radiation Physics, University of Wollongong

Dean Cutajar
Research Associate Post Doc
Centre for Medical Radiation Physics, University of Wollongong

Stuart George
Research Associate Post Doc
Centre for Medical Radiation Physics, University of Wollongong

Andrew Howie
Senior Medical Physicists
St George Cancer Care Centre, St George Hospital

Andre Bece
Radiation Oncologist Register
St George Cancer Care Centre, St George Hospital

Joseph Bucci
Radiation Oncologist
St George Cancer Care Centre, St George Hospital

Jan Jakubek
Chief scientist Advacam s.r.o
Institute of Experimental and Applied Physics, Czech Technical University of Prague

Stanislav Pospisil
Director Institute of Experimental and Applied Physics
Institute of Experimental and Applied Physics, Czech Technical University of Prague

Michael Lerch
Head of Physics
Centre for Medical Radiation Physics, University of Wollongong

Marco Petasecca
Senior lecturer
Centre for Medical Radiation Physics, University of Wollongong

Anatoly Rosenfeld
Director of CMRP
Centre for Medical Radiation Physics, University of Wollongong

Background/Purpose In high dose rate (HDR) prostate brachytherapy, accurate source placement within the prostate is vital in providing excellent dose coverage of the prostate. Current imaging techniques for seed position verification are limited in either spatial resolution or ability to provide source positioning information during treatment. BrachyView is a novel, in-body imaging system which aims to provide, high-resolution source tracking in HDR brachytherapy during intraoperative treatment. The major focus of this study was a pre-clinical evaluation of the developed real-time reconstruction software and image fusion between Transrectal ultrasound (TRUS) and BrachyView. Methods The BrachyView probe consists of a tungsten cylindrical shell with seven double cone pinholes drilled into the surface of the probe. The pinholes have a diameter of 0.5 mm with a tungsten thickness 4 mm. An edgeless quad hybrid pixilated silicon detector, Timepix is assembled and embedded within the tungsten collimator. Each detector has a size of 256 × 256 pixels, with a pixel size of 55 × 55 µm2. A full HDR treatment plan was administered within a CIRS tissue-equivalent ultrasound prostate gel phantom. TRUS was used to image the prostate. The BrachyView probe was placed in-phantom to track the HDR dwell positions in real-time. A CT scan of the experimental configuration was performed. CT data of the experimental configuration were used along with the treatment planning system to determine the planned dwell locations. Image co-registration between the BrachyView and TRUS coordinate system was also performed using the CT dataset. Results The temporal resolution of the BrachyView system showed a minimum frame rate of 0.28 s/frame, limiting source reconstruction to dwell times greater than 0.3 s, resulting in reconstruction of 175 source dwell positions out of a possible 200. Discrepancies between the planned locations and the BrachyView system were found to be within 1 mm for 78% of the 175 reconstructed dwell positions. A successful fusion between the reconstructed source locations and prostate volume was performed using the developed 3D visualisation software. Conclusion BrachyView data showed excellent agreement with the planned dwell positions with 78% of the reconstruction falling within submillimeter of their nominal location. This study shows the BrachyView system is capable of tracking the HDR source in real-time when overlaid with the TRUS images, it provides dwell position and anatomical information without the need of external radiation imaging for source position verification.


Surface Mould Treatments at the RAH

Lyndal Newmarch
Royal Adelaide Hospital
Senior Radiation Therapist

PURPOSE To give an overview of three patients treated by high dose rate brachytherapy using individualised custom-made surface moulds with 3D CT planning. METHODS AND MATERIALS Three patients with custom made surface moulds were selected to highlight the diversity in treatment techniques utilised when treating surface tumours with HDR brachytherapy at the RAH. These patients were selected to show the different methods and materials used in making the surface moulds. The first patient with recurrent SCC of the tip of nose was treated using a custom made thermoplastic applicator shaped over a plaster mould of the patients face, 39.6Gy, 4.4Gy/#, 9#s, computer planned. The second patient with recurrent SCC of the skin of the scalp was treated using a custom made wax applicator shaped over a plaster mould of the patients scalp and neck, 51.0Gy, 2.55Gy/#, 20#s, computer planned. Finally the third patient with Myxofibrosarcoma of the left anterior thigh was treated using a custom made superflab shaped over the patient’s leg, 38.5Gy, 3.85Gy/#, 10# computer planned. RESULTS Many different commercial surface moulds and applicators exist for use with a HDR Brachytherapy unit. At the RAH with custom made surface moulds utilising different techniques, materials and methods of preparation we are able provide excellent dosimetric results by tailoring the surface mould to the individual patients requirements. Thermoplastic moulds, wax moulds and superflab applicators are three techniques used at the RAH. CONCLUSIONS HDR Brachytherapy is a highly effective treatment option for treating surface and subcutaneous carcinomas. Custom made moulds make it possible to deliver a uniform dose distribution with HDR Brachytherapy, they are easy and safe to use and highly accurate for daily treatment replication.


Do we need a minimum dwell time restriction in HDR brachytherapy treatments?

Eeva Boman
Blood & Cancer Centre, Wellington Hospital
Senior Medical Physicist

Dean Paterson
radiation therapist
Blood & Cancer Centre, Wellington Hospital

Lynne Greig
Head physicist
Blood & Cancer Centre, Wellington Hospital

Background and Purpose The timer accuracy of the VariSource iX HDR brachytherapy afterloader (Varian Medical Systems, CA) is stated to be better than 1% or 0.1 second (s) whichever is greater. However, a conservative approach is applied in our centre so that dwell times <1s are manually edited to either 0 or 1s. With small doses per fraction, such as in interstitial breast treatments, and especially with a new source, this minimum dwell time restriction can be a limiting factor in achieving a good dose distribution. The aim of this study is to investigate possible errors in delivered dose when dwell times <1s are used. Methods Timer linearity was measured by positioning the source at a fixed location in a well chamber (HDR 1000 Plus with source holder 70010, Standard Imaging, WI), altering the dwell times from 60s to 0.1s and measuring charge. The differences in dose to the plan reference point for plan geometries created with and without dwell times < 1s, for the same calculated dose, were measured with a microDiamond detector (PTW, Germany). Plans without small dwell times were considered as reference plans. A single channel plan geometry used a Freiburg flab (Elekta, Netherlands) and a multichannel geometry used five needles (ProGuide 6F, Elekta). Figure 1 shows the phantom geometry and dwell times used. The plan doses were calculated with the AcurosTM BV model (Brachyvision 11.0, Varian Medical Systems). Results Results are shown in Figure 2. Timer linearity measurements resulted in a maximum difference to linear fit of 2.5% at dwell time 0.1s and -1.2% at dwell time 1s. With a 370GBq source, these timer errors would result in dose errors of 0.4mGy and 2 mGy respectively at 1 cm distance from the source. In microDiamond measurements, the maximum difference between measured values for plans containing small dwell times and reference plans was -1.3% with the plan that had ≥1s dwell times and ≤1% in the plans that had dwell times <1s. Conclusions The errors in timer linearity and dose measurements with small dwell times were all considered to be negligible in the context of total treatment accuracy. The errors were smaller with the plans containing dwell times <1s than in the plans containing 1s dwell times. It is therefore not necessary to apply a restriction to the use of small dwell times with the VariSource iX afterloader.


Salvage high dose rate brachytherapy for prostate cancer in South Australia

Hien Le
Royal Adelaide Hospital
Radiation Oncologist

Radical intent external beam radiotherapy for prostate cancer is an important option for therapy. Surveillance of these patients post therapy can detect early recurrences. In the setting of local recurrence as determined on PSMA-PET scan, high dose rate brachytherapy is a potential salvage treatment option. Here we present preliminary outcomes from patients treated in such fashion at our institution.


Optimisation and dosimetric implications of treatment parameter changes in multi-lumen balloon breast brachytherapy

Claire Dempsey
Department of Radiation Oncology, University of Washington, Seattle WA, USA
Assistant Professor

Landon Wootton
Medical physics resident
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Hannah Richardson
Dosimetrist
Department of Radiation Oncology, Seattle Cancer Care Alliance, Seattle WA USA

Myra Lavilla
Dosimetrist
Department of Radiation Oncology, Seattle Cancer Care Alliance, Seattle WA USA

Lori Young
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Juergen Meyer
Associate Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Ning Cao
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Alan Kalet
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Li-Ming Fang
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Janice Kim
Associate Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Claire Dempsey
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Background and Purpose: The Contura applicator is a multi-lumen balloon used to deliver accelerated partial breast irradiation in patients with early-stage breast cancer. It contains 5 treatment channels inside a balloon that is filled with contrast solution to compensate for tissue removed during a lumpectomy procedure. This study focused on creating optimal inverse planning parameters and assessing the dosimetric impact of rotational or treatment length changes for the resulting non-uniform dwell loadings.

Methods: Using Varian’s BrachyVision planning system, ten patients previously treated with Contura were identified. Three test plans using varying plan optimization parameters based on surface constraints were generated for each patient. Each plan underwent one round of optimization with no further modifications. Plan quality was assessed using homogeneity, conformality, planning target volume (PTV) coverage, hots spot size and maximum dose to both ribs and skin. The optimized plan was also compared to the clinical plan, which was optimized using volume constraints.

Once optimal parameters were chosen, simulated applicator rotations up to 45 degrees and treatment length variations up to 2mm were introduced into both the clinically treated plan and the newly optimised plan. Each altered plan was then assessed for plan quality to determine dosimetric effects.

Results: All 3 optimization parameter variations resulted in improvements to the PTV coverage, skin dose and hot spot size whilst maintaining dose homogeneity and conformity. Rotation of the treatment applicator inside the patient caused less than 0.5% change in PTV coverage over a 15 degree rotation with minimal difference between the clinical and more modulated optimised plan. At angles greater than 15 degrees the optimised plan produced greater changes in PTV coverage, skin and rib dose. Introducing 2mm systematic shifts in treatment length (across all channels) caused marked deviations in the dose distribution, significantly in the optimised plan. However 2mm shifts in individual channels and 1 mm systematic shifts had minimal impact on dosimetric criteria for both the clinical and optimised plans.

Conclusions: It has been shown that using surface-based optimisation criteria can improve dose distributions for single entry, multi-channel breast brachytherapy treatments. Increasing the dwell time modulation to improve dosimetry generated concern that these treatments may be more sensitive to positioning errors such as balloon rotation or discrepancies in the treatment channel lengths. Simulation of these errors indicated minimal dosimetric changes for applicator rotations of less than 15 degrees, individual treatment length changes of 2mm and systematic treatment length changes of 1mm.


Quantitative analysis of the Varian film-based position verification test using the DBSCAN clustering algorithm

Claire Dempsey
Department of Radiation Oncology, University of Washington, Seattle WA, USA
Assistant Professor

Landon Wootton
Medical Physics Resident
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Juergen Meyer
Associate Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Lori Young
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Claire Dempsey
Assistant Professor
Department of Radiation Oncology, University of Washington, Seattle WA, USA

Background and Purpose: Accurate source positioning is critical in HDR brachytherapy treatments and film based tests are typically performed to verify source position. Varian provides a device to perform this test consisting of a treatment channel in plastic with metal bars embedded in the plastic corresponding to expected dwell positions. Scatter from these bars creates dark strips on film to facilitate determination of whether the source position is within tolerance. However, in practice it can be difficult to judge the exact dwell positions on the film due to blurring, introducing uncertainty and inter-observer variation. Therefore, an image analysis program utilizing cluster analysis was developed to reproducibly and objectively determine source positions on film irradiated using a Varian supplied source position testing device.

Methods: A position verification test was performed using RT-QA radiochromic film, using the Varian source position test device. 10 dwell positions 10 mm apart were delivered with a VariSource iX HDR afterloader using an Ir-192 source. The film was scanned on a typical office flatbed scanner (HP M4555P) as a 150 dpi tiff file. The program used image thresholding to identify irradiation-induced darkening and the DBScan clustering algorithm was used to identify the 10 largest clusters of dark pixels. The actual dwell position was determined by calculating the centroid location of each cluster. Then, an intensity profile was taken on a line fit to the centroids, and the expected dwell positions were determined from this profile using a peak-finding algorithm which identified the dark strips created by the metal bars in the vendor device. The average distance between dwell positions was then calculated, as well as the maximum, minimum, and average deviation between the expected and actual positions.

Results: The algorithm correctly identified the actual and expected dwell positions on the irradiated film. The average distance between actual dwell positions was 9.9 mm. All dwell positions were within 1 mm of the expected dwell position, with an average difference of 0.5 mm and a maximum difference of 0.9 mm. Visual inspection of the film validated that these results were reasonable.

Conclusions: A programmatic method of analyzing position verification films has been developed and demonstrated to work as expected. This method provides quantitative dwell position information, eliminates inter-observer variation, and does not require a specialized scanner. Quantitative information provides robust comparison between tests performed at different times and allows trends over time to be identified.


Intracavitary vaginal brachytherapy using a custom balloon applicator

Dean Paterson
Wellington Blood and Cancer Centre
Radiation Therapist

Shelley Pearson
Radiation Therapist
Wellington Blood and Cancer Centre

Andrew Neil Wilson
Radiation Oncologist
Wellington Blood and Cancer Centre

Background and Purpose:

A custom balloon applicator was created to deliver HDR brachytherapy to a patient with a superficial vaginal carcinoma at the vaginal vault. The patient was unable to be treated with a conventional intracavitary technique, due to an extremely narrow introitus which prevented the introduction of a vaginal cylinder. Ovoids were not appropriate due to the limited treatment length they provide.

Methods:

The custom applicator was created by inserting a straight titanium tandem applicator (Mick Radio-Nuclear Instruments, NY, USA) through a Foley catheter balloon (C. R. Bard Inc, GA, USA). The tandem was inserted so the tip of the tandem was flush with the top of the balloon. The balloon inserted to the top of the vaginal vault and inflated with 45mL of contrast solution. CT (Phillips Healthcare, Netherlands) and MRI (Philips Healthcare, Netherlands) imaging was performed with the applicator in-situ prior to the first treatment insertion to determine the feasibility of the technique. CT imaging was then performed at each treatment fraction for delineation of the applicator and organs at risk. The MRI was used to evaluate tumour response to EBRT and for delineation of a clinical target volume. Individual balloon eccentricities resulted in small radial tandem offsets within the balloon for some insertions. This situation was exploited by orientating the offset in the direction of the target volume. Each plan was optimised to deliver 100% of the prescribed dose to a 5cm long reference line, placed 0.5cm from the balloon surface on the patient’s left (tumour location).

Results:

Three brachytherapy treatments were delivered using this technique. Balloon dimensions were consistent with an inter-fraction deviation of 0.1cm for length and 0.2cm for diameter. The balloon length was adequate for a treatment length of 5cm. The tandem was central in the balloon for fraction one. Radial offsets of the tandem position within the balloon, up to 3.5mm, were present for fractions two and three. Table 1 provides a summary of dosimetric quantifiers for each brachytherapy plan and for the total treatment course.

Conclusions:

The custom applicator was a viable solution that resulted in an acceptable dose distribution and was well tolerated by the patient.


Implementation of a real-time prostate HDR brachytherapy system

Ryan Brown
St George Cancer Care Centre
Medical Physics Registrar

Andrew Howie
Senior Medical Physicist
St George Cancer Care Centre

Komiti Enari
Senior Medical Physicist
St George Cancer Care Centre

Iliana Peters
PhD student
University of Wollongong

Dean Cutajar
Research Physicist
St George Cancer Care Centre

Joseph Bucci
Radiation Oncologist
St George Cancer Care Centre

Background & Purpose The aim of this project was to implement real-time HDR prostate brachytherapy at St George Cancer Care Centre using the treatment planning system (TPS) Oncentra Prostate (OCP) v4.2.2 (Elekta AB, Stockholm, Sweden). There is currently no published literature specifically discussing commissioning of real-time HDR planning systems. AAPM TG53 and IAEA TRS430 include recommendations for the commissioning of brachytherapy TPS that were utilised in the formation of a commissioning plan tailored for real-time HDR. Methods Extensive commissioning testing was performed on OCP as well as the associated sub-systems (stepper, encoder, template). The tests were designed based on recommendations in IAEA TRS430 and AAPM TG53, with some additional testing added to cover thorough testing of OCP-specific features. Peripheral testing was also carried out on the brachytherapy module of RadCalc v6.3.2 (LifeLine Software Inc, USA) for plan verification. The heavy reliance of OCP on ultrasound imaging required extensive quality assurance (QA) testing to be performed, and implemented at a higher frequency within the department, to maintain confidence. Finally, an end-to-end test was carried out and real time dose verification measurements obtained in a prostate phantom using MOSkin dosimeters, placed in 3 locations along the rectal wall. Before clinical release, a detailed multidisciplinary risk assessment was performed and extensive documentation formulated, including workflow guidelines and QA checklists. Results Initial geometric accuracy tests within OCP revealed a 10% discrepancy, requiring the ultrasound to be recalibrated within the software. Isodose distribution differences were noted in OCP when compared to the current brachytherapy TPS Oncentra Brachy (OCB). Analysis of the Flexisource data within OCP revealed some minor differences with the source data when compared to source data from published literature. Final end-to-end testing of the real-time HDR system with OCP on a prostate phantom with in vivo dosimetry yielded point measurements in agreement with OCP by less than 3.7%, and validation of the plan in RadCalc exhibited maximum point dose differences of 0.1%. Conclusions Accuracy of ultrasound calibration in the ultrasound system and in OCP is essential for providing accurate patient treatment. Additional extrapolated source data in OCP relative to the published source data can lead to small inconsistencies when compared to OCB. End-to-end testing verified, through in vivo measurement and TPS comparisons, that the set up was correct, including all calibrations, sub-systems and hardware, and that the technique was safe for clinical use.


3T MR IMAGE-GUIDED UTEROVAGINAL HDR BRACHYTHERAPY FOLLOWING INTENSITY MODULATED RADIATION THERAPY FOR CERVIX CANCER – 6 year follow-up of disease outcomes and toxicity

Mark STEVENS
Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney
Radiation Oncologist

Judith Martland
Senior Physicist
Northern Sydney Cancer Centre,Royal North Shore Hospital, Sydney

Florence Ko
Brachytherapy Radiographer
Northern Sydney Cancer Centre,Royal North Shore Hospital, Sydney

Lesley Guo
Statistician
Northern Sydney Cancer Centre,Royal North Shore Hospital, Sydney

Marita Morgia
Radiation Oncologist
Northern Sydney Cancer Centre,Royal North Shore Hospital, Sydney

Background & Purpose: To present the 6-year patterns of failure, overall survival, and detailed late toxicity outcomes of women treated with GEC-ESTRO defined adaptive MR-image guided brachytherapy (MR-IGBT) for predominantly locally advanced lymph node positive cervix cancer following intensity-modulated radio-chemotherapy.

Methods: From July 2010 to end-June 2016, 41 consecutive women with biopsy proven cervix cancer (median age 51 yrs; 25-77) were referred after FDG-PET/CT, pelvic MRI, and joint EUA staging for curative-intent EBRT and synchronous weekly platinum chemotherapy followed by MR-IGBT. 36/41 patients had FIGO Stage II (n=18) or III/IV (18) disease. All treatment was completed within 50 days. Thereafter patients were followed with 3-6 monthly clinic visits, pelvic examinations, cervical cytology and HR-HPV analysis. FDG-PET/CT were done at 3 months, 12 months, and 24 months post MR-IGBT, or as otherwise indicated.

Results: Twenty-five (61%) had positive pelvic (21) or para-aortic lymph nodes (4). Extended-field IMRT was used in 66% of cases (27). Median overall relapse-free survival (RFS) and OS was 44% and 69% respectively, at 65 months. Median GTV@diagnosis was 32.5cc (1.4-354cc ) and was reduced by 81% to 6.3cc after initial radio-chemotherapy. Further significant adaptive changes in GTV, HR-CTV and IR_CTV were noted during MR-IGBT but were not related either local or non-local relapse, or survival metrics. Local relapse was observed in only 3 patients (7%). FIGO stage was a poor predictor of RFS, DFS and OS. Any positive LN (pelvic or para-aortic) was significantly related to RFS (p=0.0007) but not OS (p=0.081) except when para-aortic LN were positive (p<0.0001). Prospective evaluation of late GI, GU, and reproductive system toxicities were recorded using NCI-CTCAE. The probability of Grade 2 or worse GI and GU toxicity-free survival was 87.5% and 90.2% at 6-years. G2 or greater reproductive system toxicities, mainly vaginal shortening and stenosis, occurred in over a third of women despite prophylactic post treatment vaginal dilation.

Conclusions: Initial complex radio-chemotherapy followed by MR-IGBT is a safe strategy for patients with advanced cervical cancer. Local disease control within the central pelvis and metastatic LN sites occurred in nearly all patients with minimal morbidity. FIGO staging (2008) alone however does not recognize positive LN status as detrimental variable reducing the OS impacts of better pelvic cancer control.


Endobronchial brachytherapy as a palliative intervention: reviewing 20 years of experience in an Australian centre

Matthew Knox
St George Hospital, Kogarah, NSW
Junior Medical Officer

Andrej Bece
Research and Clinical Fellow
Department of Radiation Oncology, St George Hospital, Kogarah, NSW

Joseph Bucci
Radiation Oncologist
Department of Radiation Oncology, St George Hospital, Kogarah, NSW

John Moses
Respiratory Physician
Department of Respiratory Medicine, St George Hospital, Kogarah, NSW

Peter Graham
Radiation Oncologist
Department of Radiation Oncology, St George Hospital, Kogarah, NSW

Background and Purpose:

Management in patients with end-stage primary and metastatic lung cancers focuses on symptom control, including airway obstruction and haemoptysis. In this context, endobronchial brachytherapy (EBB) is an approach allowing safe delivery of clinically meaningful radiation doses with evidence supporting its ability to effectively palliate symptoms.(1) EBB also has an acceptable risk of local bronchial adverse effects, whilst its sharp dose fall-off minimises non-bronchial side-effects.(2)

Use of EBB in Australia is currently infrequent and as such, local research is limited. This study attempts to provide a broad summary of the characteristics of both high dose-rate (HDR) and pulsed dose-rate (PDR) treatments in a single centre.

Methods:

This study was designed as a retrospective audit. Palliative EBB procedures performed at the St George Cancer Care Centre, NSW between 1997 and 2016 inclusive were included in the study. Records (paper and electronic) were retrospectively reviewed and data pertaining to oncological diagnosis, treatment and clinical follow-up were collected.

Data and their analysis were primarily descriptive, providing a summary of the characteristics of treatment at our unit.

Results:

95 EBB cases were identified in 86 patients, with 78 cases treated with PDR and 17 with HDR. Clinical and/or radiological airway obstruction in a prior high-dose irradiated volume was the most common indication for treatment (81%). The majority of cases involved primary lung lesions (73%), with squamous cell carcinoma (38%) the most common histological subtype.

Lesions were treated throughout the bronchial tree, though the right lower lobe bronchus (22%) and left main bronchus (17%) were the most common anatomical locations for treatment. Of the 78 patients treated with PDR, the median dose was 10 Gy (range=5-15) delivered in 10 pulses (1997-2011). Of the 17 patients treated with HDR, the median dose was 10 Gy (range=5-10) in 1 fraction (2005-2016).

Of 86 cases with documented clinical outcomes, 63 (73%) had a partial or complete response of symptoms. There was no difference in the rate of clinical response between PDR and HDR patients (p=0.202). There were no grade≥2 complications recorded.

Conclusions:

We present the largest Australian series of EBB to date. EBB is an effective approach to the palliation of symptoms in patients with malignant lung lesions. Despite a variety of symptomatic presentations, histologies and anatomical locations, the majority of patients in our study experienced an improvement in reported symptoms. Given its low risk of toxicity,(2) EBB should continue to be considered an option in the palliative treatment of lung malignancies.

References:

1) Tofts RP, Lee PM, Sung AW. Interventional pulmonology approaches in the diagnosis and treatment of early stage non-small-cell lung cancer. Transl Lung Cancer Res. Oct 2013; 2(5):316-31

2) Nguyen NTA, Sur RK. Brachytherapy in lung cancer: a review. Transl Cancer Res. Aug 2015; 4(4):381-96


Accounting for previous radiotherapy treatments using deformable image registration: A case study in prostate brachytherapy

Johnson Yuen
St. George Hospital, Cancer Care Centre
Medical Physicist

Andrew Howie
Medical Physicist
St. George Hospital, Cancer Care Centre

Ryan Brown
Medical Physicist
St. George Hospital, Cancer Care Centre

Dean Cutajar
Research Physicist
Centre for Medical Radiation Physics, University of Wollongong

Andrej Bece
Radiation Oncologist
St. George Hospital, Cancer Care Centre

Joseph Bucci
Radiation Oncologist
St George Cancer Care Centre

Background and Purpose

Deformable image registration(DIR) allows for the summation of doses from multiple radiation treatment deliveries to accounts for previous treatment –assessed to be frequently missed and hard to detect by TG100[1]. High dose rate (HDR) brachytherapy treatments involving multiple fractions were assessed using the Brachytherapy Treatment Planning System (BTPS) Oncentra Brachy and DIR software (MIM). Recommendations for optimisation of this process have been developed, which provide a framework to account for multiple treatments in brachytherapy, extending to treatments that include external beam radiotherapy plans.

Methods

Both rigid and deformable registration were performed for HDR brachytherapy procedures involving multiple fractions, with the newer fraction set as the primary dataset. Deformable registrations were subject to user optimisation. Registration QA analysis with the Dice similarity coefficient and mean distance to agreement for both registrations were compared, indicating spatial error. Dose volume histogram and dose constraints for the urethra, rectum, and target were evaluated.

Results

The assessment of HDR brachytherapy treatments involving multiple fractions was successful. Commissioning results from BTPS to the DIR software revealed inherent sampling errors in the DVH metrics. Deformable registration QA reduced spatial error compared to rigid registration and DIR error can be dependent on user optimisation[2]. The effect of DIR errors on DVH metrics were assessed. Limitations of this technique were identified which include factors such as variations in contouring, changes in organ, and radiobiology considerations.

Conclusions

Dose accumulation with DIR can offer superior results to rigid registration in terms of spatial errors which translate to improved accuracy of dose metrics in DVHs. Clinical use of dose accumulation of multiple treatments was demonstrated in the department with scripted reports based on patient-specific QA that include estimated errors as well as a list of residual limitations. These investigations form the framework for arbitrary accounting for treatments to and from external beam plans with dose.

References

1. Huq, M.S., et al., The report of Task Group 100 of the AAPM: Application of risk analysis methods to radiation therapy quality management. Medical Physics, 2016.

2. Johnson, P.B., et al., Evaluation of the tool “Reg Refine” for user-guided deformable image registration. Journal of Applied Clinical Medical Physics, 2016. 17(3).


Moulds and cylinders: Clinical quality and dosimetric analysis of an adjuvant image-guided intra-vaginal brachytherapy (IVBT) programme for endometrial cancer

Florence Ko
Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney
Brachytherapy Radiographer

Judith Martland
Senior Physicist
Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney

Tony Lee
Senior Mould Room Technician and Radiographer
Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney

Mark STEVENS
Radiation Oncologist
Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney

Lesley GUO
Statistician
Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney

Background and purpose: Adjuvant vaginal vault (cuff) brachytherapy has emerged as an important evidence-based treatment modality for women with early stage intermediate and high-risk endometrial cancer. In June 2010 we initiated a pilot “first fraction” CT-based IVBT programme to select women best treated with a customized vaginal mould. Critical quality variables for use of a mould versus cylinder-based IVBT included,

(1) Vaginal mucosa-to-cylinder conformance and dosimetric perturbations within the HR-CTV induced by air gaps,

(2) DVH analysis of HR-CTV D90 coverage and vaginal mucosa, rectal and bladder exposures.

Methods: An algorithm was generated for selection of patients for vaginal brachytherapy administered by either a "best-fit" standard single-channel rigid cylinder applicator or a customized multi-channel vaginal mould implant. During a 9 month period from June 2010, 18 consecutive women with endometrial cancer were enrolled. First fraction CT planning (Oncentra v3.3) occurred with empty bladder and rectal flatus tube in situ. IVBT delivered either 1200 cGy in 2 fractions (n=3) or 3000 cGy in 6 fractions (n=10) over 1-3 weeks at 3 or 5 mm mucosal depth. A further cohort of 60 IVBT patients have been additionally studied to end July 2014 using a modified Institut Gustav Roussy (IGR) method of vaginal mould construction.

Results: Four patients (4/13; 31%) in our pilot group required customized multi-channel vaginal mould IGVBT. One woman had disturbed vault topography (congenital duplication) and 3 patients had >80% (mean 85%) point perturbations in prescribed dose due to air gaps within the HR-CTV. Average vaginal mucosal displacement (“radial” non-conformance) was 5.1 mm (4.2-6.2 mm) and the number of air gaps ranged from 3 to 4. Respective median vaginal, rectal, and bladder D2cc were within GEC-ESTRO GYN guidelines and were later correlated with toxicity in a DVH and outcomes study of the entire series (n=78).

Conclusions: IVBT is a sophisticated care standard in endometrial cancer. Up to a third of patients may require dose delivery by customized multi-channel vaginal mould. Australian radiation oncology departments performing IVBT should be appropriately resourced with enhanced brachytherapist and mould room competencies