Reporting Vaginal Dose Point in Cervical Cancer Patients of Asian Origin Treated With Combine 3D External Beam Radiotherapy and 3D Brachytherapy and Comparing It With a Caucasian Population - Is There a Difference?

Abstract

Purpose: To investigate the clinical feasibility and treatment outcomes of image-based high dose rate (HDR) brachytherapy using an intracavitary multichannel vaginal cylinder for the definitive treatment of vaginal cancers Materials and Methods: Forty-one patients with vaginal cancer (24% primary vaginal, 76% recurrence from other gynecologic primaries) treated with definitive radiotherapy chemotherapy including imagebased HDR brachytherapy with a multichannel vaginal cylinder. Imagebased brachytherapy was completed using either CT-based (41%) or MR-based planning (59%) with each fraction. The high-risk clinical target volume (HR-CTV) was defined based on the preand post-external beam radiotherapy GTV (see Figure). Doses were converted to equivalent dose of 2Gy per fraction (EQD2Gy). Endpoints examined: dose-volume parameters and early clinical outcomes. Results: The median HR-CTV volume was 24.2cc [Interquartile range (IQR): 12.6], with a median dose to 90% (D90) of 77.1Gy (IQR: 3.4). The median dose to 2cc (D2cc) for the bladder, rectum, and sigmoid were 59.4Gy (IQR: 5.6), 58.2Gy (IQR: 4.1), and 52.3Gy (IQR: 5.5) respectively. After a median follow-up of 16 months (range: 3-35), complete clinical response was documented in 98% of patients. The 2year local control, regional control, distant control, disease free survival and overall survival were 93%, 100%, 81%, 78% and 88%. The 2-year actuarial rate of late $ grade 3 toxicity was 4% overall with 0% vaginal, 0% bladder, urethral 0%, and 4% gastrointestinal, respectively. Conclusions: Image-based HDR brachytherapy using an intracavitary multichannel cylinder appears feasible in definitive vaginal cancer treatment. The described clinical implementation of image-based multichannel cylinder brachytherapy, including concepts of HR-CTV delineation, patient selection, and dose-constraints show promising early clinical outcomes with high rates of local control and little toxicity which should be validated with extended follow-up.