Comparison of vaginal stenosis following vault brachytherapy monotherapy between common fractionation schemes in the treatment of endometrial cancer
Vaginal stenosis is a well-documented toxicity of vaginal brachytherapy (VBT), which can lead to impaired quality of life and difficulty with surveillance pelvic exams. While multiple dosing and fractionation schemes have proven efficacy at preventing local recurrence, the comparative rates and severity of vaginal stenosis is not well-documented. This study aims to evaluate the rate of vaginal stenosis in patients with endometrial cancer treated with 2 common high-dose rate (HDR) adjuvant VBT without external beam radiation (EBRT) using vaginal cylinders. A retrospective review of patients treated at a single institution with adjuvant VBT following hysterectomy for uterine cancer was performed. The 2 regimens evaluated were 21 Gray (Gy) delivered in 3 fractions (fx) prescribed to a depth of 5 mm, delivered once weekly, and 30Gy/5fx prescribed to the vaginal surface, delivered every other day. Patient demographic and treatment information was collected from electronic medical records, including patient age at the time of treatment, BMI, cancer histology, chemotherapy status, common terminology criteria for adverse events (CTCAE) grade of vaginal stenosis, cylinder size, treatment length, sexual activity, and subsequent dilator use. Bivariate analysis was completed using Odds Ratios and χ2 tests with KNIME software version 5.4.0. Of the 150 patients treated with VBT between 2018 and 2024, 92 received cuff brachytherapy alone with a single-channel cylinder, utilizing either 30Gy/5fx or 21Gy/3fx. Of these patients, 88 were available for at least 3 months of follow-up with median follow-up of 23 months. Median patient age was 66 years. Seventy-two (82%) patients were white and 47 (53%) patients received chemotherapy. Thirty-three patients received 21Gy/3fx (38%) and 55 patients received 30Gy/5fx (62%). Vaginal stenosis was reported in 54% of patients who received 21Gy/3fx, compared to 22% of those who received 30Gy/5fx (OR 4.3 [95% CI: 1.7-11.0, p = 0.002]). Most patients in each group had common terminology criteria for adverse events (CTCAE) grade 1 stenosis (90% in 21Gy/3fx-group and 67% in 30Gy/5fx-group). The median cylinder size was 30 mm, and the mean treatment length was 5 cm, neither of which appeared to affect risk of developing vaginal stenosis (OR 1 [95% CI: 0.4-2.5, p = 1] and OR 1.4 [95% CI: 0.5-3.4, p = 0.6, respectively). Receipt of adjuvant systemic therapy had a numerical, but not statistically significant increase in risk of developing vaginal stenosis (OR 2.3 [95% CI: 0.9-5.7, p = 0.1]). The risk of developing vaginal stenosis in the absence of sexual activity following completion of therapy was not significant (OR 2 [95% CI: 0.6-7, p = 0.3]), and this was true also for vaginal dilator utilization (OR 1.2 [95% CI: 0.5-3, p = 0.8]). Diagnosis with a high-risk histology did not impact risk of stenosis (OR 1.5 [95% CI: 0.6-3.6, p = 0.5]). Finally, age and BMI did not appear to affect stenosis rates (OR 1.1[95% CI: 0.4-2.6, p = 1] and OR 1.4 [95% CI: 0.6-3.4, p = 0.5], respectively). Our findings suggest that treatment with 21Gy/3fx prescribed to 5 mm depth increased the risk of developing vaginal stenosis compared to 30Gy/5fx prescribed to surface. Patient age, BMI, cancer histology, receipt of systemic therapy, sexual activity, dilator use, treatment length, and dilator size did not appear to affect the odds of stenosis. Further prospective data would be beneficial.
