This study assessed the efficacy of chemoradiotherapy for squamous cell carcinoma of the anal canal (SCCAC). Patients with T1–4N0-3M0 SCCAC received chemoradiotherapy with 5-fluorouracil (5-FU, 800 mg/m2/day, 96-h infusion) and mitomycin-C (MMC, 10 mg/m2 bolus). Patients treated with 3-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) were administered 36.0 Gy in 20 fractions or 49.5 Gy in 33 fractions for elective nodal irradiation and 59.4 Gy in 33

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... s for primary tumor and metastatic nodal irradiation. The sample size was considered sufficient to estimate 95% confidence intervals (CIs) for the true 2-year disease-free survival (DFS) within a width of +15% when the expected true 2-year DFS was 70%. The primary endpoint was 2-year DFS. The secondary endpoints were 2-year overall survival (OS), locoregional control (LC), colostomy-free survival (CFS) and adverse events. Thirty-one patients were enrolled between January 2014 and July 2019. The median follow-up was 33.3 months (range, 16.2–65.8 months). Among the 31 patients, 13%, 32%, 16% and 39% had stage I, II, IIIA and IIIB disease, respectively. Thirty patients were treated with IMRT. Complete response (CR) was achieved in 27 patients. The 2-year DFS, OS, LC and CFS rates were 77.4% (95% CI, 58.4–88.5%), 93.5% (95% CI, 76.6–98.3%), 83.9% (95% CI, 65.5–92.9%) and 80.6% (95% CI, 61.9–90.8%), respectively. One patient experienced grade 3 late adverse events; however, no grade ≥ 4 late adverse events occurred. Good DFS with a low rate of late adverse events was observed. Chemoradiotherapy with 5-FU and MMC was effective for SCCAC.