3568 - Efficacy and Safety of Brachytherapy in Primary Vaginal Carcinoma

I. Sidibe¹, D. Carignan², M. A. Froment^1,2, F. Bachand^1,2, E. Vigneault^1,2, S. Aubin³, L. Beaulieu^2,3, and W. Foster^1,2; ¹CHU de Québec – Université Laval, Radiation Oncology, Québec, Canada, Quebec, QC, Canada, ²CRCHU de Québec and Centre de recherche sur le cancer de l’Université Laval, Québec, Canada, Quebec, QC, Canada, ³Département de physique, de génie physique et d’optique, Université-Laval, Québec, Canada, Quebec, QC, Canada

Purpose/Objective(s): The aim of this study was to assess the outcome and toxicity of brachytherapy in the treatment of primary vaginal cancer. Materials/

Methods: In a retrospective analysis, 38 patients underwent treatment for vaginal carcinoma, and 4 were treated for carcinoma of Bartholins gland using brachytherapy between 2010 and 2023. External beam radiation therapy (EBRT) was administered to 41 out of 42 patients, with a median dose of 45 Gy in 25 fractions. Concurrent chemotherapy was used in 29 patients. Endocavitary (3 single channel and 3 multichannel) brachytherapy alone was utilized in 6 of the 42 patients while 36 received interstitial brachytherapy. Most patients had a combination of vaginal cylinder and interstitial catheters, inserted under Transrectal Ultrasound (TRUS) and/or TransVaginal Ultrasound (TVUS) guidance. Brachytherapy planning was based on CT with MRI fusion. We used Inverse Planning Simulated Annealing (IPSA) to plan all cases and a class solution was developed to minimize high-dose points in the vaginal mucosa while maintaining the majority of the high dose inside the cylinder. Acute (<6 months) and late genitourinary (GU), gastrointestinal (GI), and vaginal toxicities were assessed using the Common Terminology Criteria for Adverse Events version 5 (CTCAE v5). Local control (LC), metastatic disease-free survival (mDFS), and overall survival (OS) were analysed through Kaplan-Meier survival curves.
Results: The mean age was 68.9 years old, with a median follow-up of 50.5 months (3-168 months). 30 patients had squamous cell carcinoma (SCC), 6 adenocarcinoma, 3 clear cell carcinomas, 1 melanoma, and 2 gastric-type adenocarcinomas. FIGO stages was as follow: I (10%), II (71%), III (12%) and IV (7%). LC rates at 3 and 5 years were 86% and 82%, mDFS rates were 84% and 80%, and OS rates were 80.6% and 67.2%, respectively. When limited to SCC only, LC rates at 3 and 5 years were 92.2% and 92.2%, mDFS rates were 83.8% and 78.8%, and OS rates were 77% and 72%, respectively. Only 6 local relapses were recorded, with no late G3-4 GU/GI toxicity reported. Acute and late G3 vaginal toxicity (stenosis) occurred in 19% and 35% of patients, respectively. Three cases of vaginal necrosis and 2 suspicions of fistula were reported. 2 cases of vaginal necrosis were associated with local disease progression, except for one case where necrosis was limited and healed spontaneously. One patient required Hyperbaric Oxygen Therapy (HBOT).
Conclusion: brachytherapy demonstrates excellent local control in primary vaginal cancer, particularly in SCC, with favorable toxicity profile. Only mild GU and GI toxicities were observed. We observed G3 vaginal stenosis in a third of our patients and necrosis in the absence of disease progression in only 1 patient.