Intra-cavitary brachytherapy in endometrial carcinoma: experience with cobalt-60 source

To report vaginal cuff brachytherapy (VCB) dosimetry parameters and clinical outcomes of patients with localized endometrial cancer treated with adjuvant high-dose-rate (HDR) brachytherapy using a cobalt-60 (⁶⁰Co) source.

Between 2011 and 2017, we identified patients with endometrial cancer treated with surgery and adjuvant VCB. Dosimetry variables analyzed included D_2cc, D_1cc, and D_0.1cc for organs at risk (OARs) and distance from cylinder surface to 150% and 200% isodose line in vaginal mucosa. Local relapse (LR), regional relapse (RR), distant metastasis (DM), progression-free survival (PFS), and overall survival (OS) were analyzed using Kaplan-Meier, and log-rank test was applied to assess differences between groups. Toxicity evaluation was tested for possible cross-correlation within dosimetric parameters using Pearson r test and stepwise multivariate linear regression.

We identified 93 suitable patients. Mean age at diagnosis was 66 years (range, 45-85 years). Most patients had endometrioid adenocarcinoma (61.3%), followed by papillary-serous carcinoma (11.8%). 71% of patients presented with FIGO stage I (35.5% IA and 35.5% IB), 11.8% were stage II, and 17.2% were stage III. Adjuvant external beam radiotherapy (EBRT) (range, 46-50.4 Gy) was used in 53.8% of patients, and adjuvant chemotherapy in 38.7%. Median follow-up was 39 months (range, 5-84 months). Three-year OS and PFS were 87.5% and 85.5%, respectively. LR was seen in 2.2% of cases, RR in 7.5%, and DM in 12.9%. Mean rectum D_2cc/D_0.1cc were 88.1% and 116%, and mean bladder D_2cc/D_0.1cc were 79.2% and 103.2%, respectively. The most common acute toxicity was vaginal mucositis (8.9% ≥ G2), and the most frequent chronic toxicity was vaginal stenosis (25.3% ≥ G1).

Adjuvant high-dose-rate VCB with ⁶⁰Co source for patients with endometrial cancer is well tolerated, with clinical and toxicity outcomes comparable to those reported with iridium-192 (¹⁹²Ir) source.