Adjuvant Electronic Brachytherapy For Patients With Endometrial Cancer.

Brachytherapy plays a fundamental role in the adjuvant treatment of endometrial cancer (EC) to decrease vaginal cuff recurrence. Traditionally high dose rate (HDR) brachytherapy with Iridium 192 (Ir-192) had been used, but the recent development of electronic brachytherapy (eBT) based on X-ray emissions could be an alternative. Our objectives are to analyze the local recurrence in EC treated with eBT, toxicity profile and to compare with series from the literature with HDR Ir-192 brachytherapy. From September 2015 to January 2019, 271 patients with endometrial cancer were treated with vaginal eBT at our institution. 117 patients received vaginal eBT as monotherapy and 154 as a boost after external beam radiation therapy (EBRT). We used different dose-fractionation schedules: total dose was 15 Gy in 3 fractions or 14 Gy in 2 for eBT as a boost to EBRT; and 25 Gy in 5 fractions or 21 Gy in 3 fractions for exclusive eBT. Acute and late toxicities were recorded using Common Terminology Criteria for Adverse Events (CTCAE) v4.0. Data was collected retrospectively. The median follow-up was 24 months. The average age was 66 years. 70% were diagnosed as endometrioid carcinoma (Type I). According to the International Federation of Gynaecology and Obstetrics (FIGO) classification: 30% FIGO IA; 39% FIGO IB and 31% FIGO ≥IIA. Acute toxicity: 33% had vaginal toxicity; 10% had urinary toxicity; 8% had rectal toxicity and all of them were ≤Grade 1 (G1) or G2. G1-G2 chronic toxicity was observed: 10% vaginal toxicity; 1% urinary toxicity; 8% rectal toxicity; 3 patients (1.5%) had G3 rectal late toxicity. A statistically significant difference was found in the rectal toxicity observed at the patients treated with EBRT plus eBT versus eBT as monotherapy (p = 0.008). 8 patients had locoregional recurrence, 8 had systemic recurrence and 12 had both recurrences. Only 1 vaginal cuff relapse was observed. Our series, shows an increase in acute G1 vaginal mucosa toxicity with respect to HDR Ir-192 brachytherapy (33% vs 15.8%), but reduction of late vaginal mucosal toxicity (10% eBT vs. 23% Ir-192). Vaginal cuff recurrence results were better than the literature (0.36% eBT vs. 0.7-1.4% Ir-192). eBT at endometrial cancer is a feasible alternative to HDR brachytherapy with Ir-192 in effectiveness with an acceptable grade 1 acute toxicity. It has given long-term benefits for patients, providing the same dosimetric coverage in the area of treatment as HDR brachytherapy with reduction in the dose of organs at risk, benefits for staff and health system as mobility, versatility and ease of installation of the equipment. Further research is needed to establish eBT as an alternative to high dose rate brachytherapy.