Outpatient-based high-dose-rate interstitial brachytherapy for gynecologic malignancies

Purpose: To evaluate outpatient-based high-dose-rate (HDR) interstitial brachytherapy (ISBT) in the treatment of gynecologic malignancies. Methods and Materials: Between December 2006 and July 2012, 50 patients were treated with twice-daily outpatient-based HDR iridium-192 ISBT at our institution. Thirty-two patients had vaginal cancers, 13 vulvar, 3 urethral, and 2 cervical cancers. The most common histologies were squamous cell carcinoma (58%) and endometrioid adenocarcinoma (26%). Twenty-six patients were treated with definitive radiation therapy with or without platinum-based chemotherapy, 16 were treated for recurrent disease, 5 were treated in the postoperative setting, and 3 were treated palliatively. Forty patients received external beam radiation therapy before ISBT. Results: Median followup was 13.7months. Median interstitial dose was 18Gy in 2.25Gy twice-daily fractions prescribed to the implant volume. Median external beam dose was 50.4Gy in 1.8Gy daily fractions prescribed to the primary disease site. Eight patients (16%) were seen in the emergency room or were admitted to the hospital during treatment. Six patients (17%) experienced significant complications after treatment (3 ulcerations at the primary site, 1 vaginal necrosis, 1 vaginal abscess, and 1 patient with urinary obstruction). Larger volume encompassing 100% of the prescribed dose was correlated with significant complications on multivariate analysis (. p=0.039). Actuarial local control at 1year was 72%, with univariate analysis demonstrating worse local control for nonendometrioid adenocarcinoma compared with squamous cell carcinoma (20% vs. 84%, p=0.044). Conclusions: Outpatient-based HDR ISBT is feasible and safe, with toxicity and local control rates consistent with historical outcomes.