Intensity-modulated radiotherapy and cisplatin-based chemotherapy for anal cancer: long-term outcomes at a single institution

Purpose: To evaluate oncological outcomes and late toxicities in a retrospective series of patients with locally-extended anal squamous cell carcinoma (ASCC), treated with curative Intensity Modulated Radiotherapy (IMRT) and chemotherapy. Methods: ASCC patients who underwent chemo-radiotherapy with IMRT from 2010 to 2020 were included. Oncological outcomes were assessed in terms of overall survival (OS), disease-free survival (DFS), colostomy-free survival (CFS) and event-free survival (EFS). Late toxicity was detected according to CTCAE v.5.0 and RTOG late radiation morbidity scoring system. Results: Ninety-five patients were included. Most patients (83%) received chemotherapy with oral Fluoropyrimidine plus Cisplatin. The median follow-up was 5.5 years. The OS was 85.2%, 82.1% and 79.3% at 3, 5 and 8 years, respectively. The DFS was 73.1%, 70%, and 65.3% at 3, 5 and 8 years, respectively; 3, 5 and 8 years CFS was 86.2%, 84.3% and 84.3%, respectively. The EFS was 71%, 67.9% and 63.1%, at 3, 5 and 8 years, respectively. On univariable analysis, a statistically significant lower OS was found for patients with T3-T4 stage (HR = 4.58, p = 0.005) and overall treatment time (OTT) ≥ 47 days (HR = 3.37, p = 0.038). A statistically significant lower DFS was reported for patients with T3-T4 stage (HR = 2.72, p = 0.008) and Serum Squamous Cell Carcinoma Antigen (SCC) value post-RT > 1.5 (HR = 2.90, p = 0.038.). Ten severe late toxicity (≥ G3) events were reported in 8 patients (8.6%). Conclusions: Our data confirm IMRT concomitant with a Cisplatin-based chemotherapy as an effective treatment of ASCC, ensuring acceptable long-term toxicities and good oncological outcomes.