Low-Dose Adjuvant Cylinder Brachytherapy for Endometrioid Endometrial Cancer

Purpose: Our purpose was to evaluate outcomes and sites of failure for women with early stage endometrial adenocarcinoma treated with adjuvant high-dose-rate (HDR) vaginal brachytherapy (VB) with a low dose scheme.

Methods and materials: Retrospective review identified 318 patients with International Federation of Gynecology and Obstetrics (FIGO) stage I-II endometrioid endometrial cancer who received adjuvant HDR VB to a dose of 24 Gray (Gy) in 6 fractions from 2005 to 2017. Patients with <6 months follow-up were excluded. Dose was prescribed to cylinder surface and computerized tomography (CT) imaging was performed before each fraction to assess cylinder placement. Rates of vaginal relapse (VR), pelvic nodal relapse, distant metastasis, recurrence-free survival, and overall survival were calculated by Kaplan-Meier method. Univariate analysis was performed by log rank test or Cox proportional hazards. Pretreatment CT images were analyzed for patients with VR.

Results: Median follow-up was 42 months for 243 patients. The 3-year rates of VR, pelvic nodal relapse, distant metastasis, recurrence-free survival, and overall survival were 1.9%, 1.5%, 4.3%, 94.1%, and 98.9%, respectively. The 3-year VR rates by Gynecologic Oncology (GOG)-99 risk groups were 0%, 1.4%, and 3.2% for low risk, low-intermediate risk, and high-intermediate risk (HIR) disease (P = .5). By Post-operative Radiation Therapy in Endometrial Carcinoma (PORTEC) risk stratification, 3-year VR rate was 1.3% for HIR disease. On review of pretreatment CT images of the 6 patients with VR, 3 patients had relapse at the introitus outside of the treated vaginal length, and 3 had in-field recurrence at the vaginal apex. Higher body mass index (BMI) was associated with VR, with a 14% increase in risk per BMI unit (kg/m², P = .02). There were no reported grade 2 GI or any grade 3 toxicities.

Conclusions: Adjuvant HDR VB with a low-dose regimen results in excellent clinical outcomes for patients with early stage endometrioid endometrial cancer. Patients with higher BMI may be at increased risk of VR, and additional study is needed to optimize brachytherapy treatment parameters.