Long-term outcomes and toxicities of a large cohort of anal cancer patients treated with dose-painted IMRT per RTOG 0529

Purpose To describe the outcomes and toxicities of the largest cohort to date of patients with anal squamous cell carcinoma uniformly treated with concurrent chemoradiation using dose-painted intensity modulated radiation therapy (DP-IMRT) according to RTOG 0529.Methods and materials We identified 99 eligible patients with anal cancer who were treated at our institution with definitive chemoradiation using DP-IMRT between 2005 and 2015 per RTOG 0529 dosing guidelines. Primary study endpoints included event-free survival (defined as recurrence, colostomy, or death) and overall survival. Secondary endpoints were treatment duration and acute and late toxicity.Results At a median follow-up of 49 months (range, 2-114 months), 92% of patients had a clinical complete response. Fifteen percent underwent colostomy, including 4 pretreatment colostomies, 6 planned abdominoperineal resections (APRs), 4 salvage APRs, and 1 APR for treatment-related complications. Thirteen patients developed local recurrence, of whom 6 developed synchronous metastatic disease. The 4-year overall survival was 85.8%, and 4-year event-free survival was 75.5%. Median treatment duration was 43 days (range, 10-68 days). The overall rate of non-hematologic grade 3+ acute and grade 2+ late toxicities was 20% and 15%, respectively.Conclusions Long-term outcomes and tolerability were excellent In the largest cohort to date of patients with anal cancer who received DP-IMRT prescribed per RTOG 0529.