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


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