This retrospective cohort study included 116 breast cancer patients who underwent mastectomy and pre-pectoral implant-based breast reconstruction (PP-IBBR) followed by radiotherapy with either photon (n=75, 64.7%) or proton (n=41, 35.3%). Fewer complications were found the proton group. Major infection, minor infection, delayed wound healing, partial flap necrosis, seroma development, re-operations, implant failure, and capsular contracture of all grades as well as grade 3 and 4 capsular contracture were seen more in the photon group. The authors concluded that proton is a safer option, warranting larger studies and broader utilization in clinical practice.