Intensity-modulated radiotherapy (IMRT) in the treatment of squamous cell anal canal cancer: acute and early-late toxicity, outcome, and efficacy

Purpose: To retrospectively review our experience on 84 patients with squamous cell anal canal cancer (SCAC) within 12 months after combined treatment with intensity-modulated RT (IMRT), in terms of acute and early-late toxicity, overall treatment time and interruptions, colostomy-free survival (CFS), and tumor response. Methods: Acute gastrointestinal (GI), genitourinary (GU), and cutaneous (CU) toxicities were assessed according to Common Toxicity Criteria for Adverse Events (CTCAE) version 4.03. Early-late toxicity was scored using the Radiation Therapy Oncology Group (RTOG) late radiation morbidity scoring system. Tumor response was evaluated with response evaluation criteria in solid tumors (RECIST) v1.1. Results: Acute toxicity for 84 subjects (100%): severe (≥ G3) GI and skin toxicity was observed in 4 (5%) and 19 patients (23%), respectively. Early-late toxicity for 73 subjects (87%): severe (≥ G3) GI and vulvo-vaginal toxicity was observed in 2 (3%) and 2 (3%) patients, respectively. No acute or early-late severe GU toxicity was reported. A treatment interruption occurred in 65 patients (77%). CFS was 96% (95% CI 89–99) at 6 months and 92% (95% CI 83–96) at 12 months. At 6 months complete response (CR), partial response (PR) and progressive disease (PD) was observed in 70 (83%), 3 (4%), and 7 patients (8%), respectively. At 12 months, CR was observed in 60 patients (81%); eleven patients (15%) experienced PD. Conclusion: Our study showed an excellent clinical result and very low acute toxicity rates, confirming the IMRT as standard of care for curative treatment of anal cancer patients. The current trial was registered with the number IEO N87/11