Long-Term Results Following Use of Vaginal Electronic Brachytherapy in the Management of Endometrial Cancer

Abstract

<h3>Purpose/Objective(s)</h3> We evaluated long-term vaginal toxicity and disease outcomes in women treated with vaginal electronic brachytherapy (EBT) following surgical management of endometrial cancer. <h3>Materials/Methods</h3> Women with endometrial cancer treated with adjuvant EBT were included in this study. Women diagnosed with uterine cancer of high-risk histology or advanced stage received EBT following completion of adjuvant chemotherapy. EBT was performed using a miniature low-energy (50-kV peak) X-ray source with a single-channel vaginal cylinder applicator to deliver radiation to the vagina along a specified length of the cylinder. EBT was delivered either as monotherapy or as a sequential boost following completion of pelvic external beam radiation (EBRT). EBT was delivered to 4 cm treatment length prescribed as 7 Gy to 5 mm depth x 3 fractions in the EBT alone group or 6 Gy to vaginal surface x 3 fractions in the EBT boost group. Following completion of EBT, patients were evaluated for all toxicities and recurrences. In this study, we evaluated for treatment related vaginal toxicity (stenosis) which was scored according to the Common Terminology Criteria for Adverse Events version 5.0. Multivariable analysis (MVA) of prognostic factors was performed using Cox Proportional-Hazards Model, and disease-free survival (DFS) and overall survival (OS) were estimated from date of surgery with Kaplan-Meier Method using data management and decision management software. <h3>Results</h3> 70 women were treated from 12/2017-6/2020 with EBT following hysterectomy. Median age of the cohort was 68 years (range, 51-85 years). 37 presented with endometrioid histologies. 32 received adjuvant chemotherapy prior to EBT. 21 presented with stage II or greater disease, and 20 received EBRT prior to EBT boost. EBT was delivered over a median interval of 1.3 weeks (range, 0.3-3.1 weeks). At a median follow-up of 25.0 months (range, 7.2-47.4 months), no patients were found to have ≥ grade 3 vaginal toxicity. The cumulative risk of developing gr 1 and 2 vaginal toxicity at 30 months was 25%. Prescription to 5 mm depth was the only factor associated with development of vaginal toxicity (p<0.05). One vaginal cuff recurrence, one locoregional recurrence, and ten distant recurrences were observed. Advanced tumor stage, high-risk histology, cervical stroma involvement, treatment with chemotherapy, and treatment with EBRT were significantly associated with inferior DFS/OS on MVA. DFS and OS in this group at 12 and 36 months were 94.2%/69.4% and 95.7%/88.3%, respectively. <h3>Conclusion</h3> EBT appears to be a safe, well-tolerated, and a promising alternative treatment option to traditional vaginal brachytherapy using a radioactive source. On MVA, prescription of EBT to 5 mm depth was associated with vaginal stenosis. One local recurrence was observed at 25 months follow-up. Risk of developing vaginal toxicity, DFS, and OS, following treatment with EBT in this heterogeneous population appear to be acceptable and comparable to historical controls (PORTEC 2 PMID 20206777).