This multi-institutional study compared late toxicity profiles of a total of 1850 patients, including 1282 IMRT and 568 PBT. Overall toxicity rates were low, with the majority of patients experiencing no late GU (56.6%, n=1048) or late GI (74.4%, n=1377) toxicity. No difference was seen in the rates of late toxicity between the groups, with late Grade 3+ GU toxicity of 2.0% vs 3.9%, and late Grade 2+ GI toxicity of 14.6% vs 4.7%, for the PBT and IMRT cohorts respectively.