This study reported toxicity of 14 patients with anal cancer treated with chemoradiation using IMPT. Rates of physician-reported GI, GU, dermatologic, and hematologic toxicity were not significantly different between patients treated with IMPT compared with patients treated with IMRT. The authors concluded that physician-reported toxicity was not improved with IMPT in the context of this underpowered trial. High-grade GI symptoms persisted for 12 months and were similar to baseline.