Low-dose-rate interstitial brachytherapy boost for the treatment of anal canal cancers.

PURPOSE: Evaluate the efficacy and tolerance of interstitial brachytherapy (IBT) after external beam radiotherapy (EBRT) or radio chemotherapy (RCT) for the treatment of anal canal cancers (ACC).

METHODS AND MATERIALS: From 01, 1990 to 01, 2013, 103 patients (p) with ACC were treated with IBT after EBRT or RCT at our institution. Tumor node metastasis stage included Tis (1 p), T1 (18 p), T2 (46 p), T3 (33 p), and T4 (5 p). There was a lymph node involvement in 19 p. Ninety-nine patients presented with squamous cell carcinoma (95.5%) and seven with adenocarcinoma (4.5%). The median EBRT dose was 45 Gy (18-65 Gy). Thirty-nine patients (37.86%) received concomitant RCT. IBT was performed 0.9 months (0-4.38) after RCT or EBRT. The median IBT dose was 17.2 Gy (10-30 Gy).

RESULTS: Within 4.8 years of followup, 15 p (14.6%) had an abdominoperineal amputation with definitive colostomy (11 p had locoregional failure, and 4 p had anal incontinence). Late toxicity was presented in 40 p (38.8%). Overall survival rates of 99% at 1 year, 89.4% at 3 years, and 85.7% at 5 years, and 1-year, 3-year, and 5-year local control rates of 97.9%, 95.4%, and 89.1%, respectively. The 1-year, 3-year, and 5-year colostomy-free rates were 98.9%, 94.0%, and 86.4%, respectively. No factors in the multivariate analysis were associated with the overall survival or any failure type.

CONCLUSIONS: IBT boost provides excellent local control with low colostomy rates and a late toxicity profile in ACC treatment.