This is the trial protocol of RadComp. This multi-center trial sets the objective to evaluate whether the differences between proton and photon therapy cardiac radiation dose distributions lead to meaningful reductions in cardiac morbidity and mortality after treatment for breast cancer, hypothesizing that the 10-year estimate major cardiovascular events (MCE) rate of 3.5% for the proton arm as compared to that of 6.3% of the photon arm.

A total of 1278 patients with non-metastatic breast cancer will be randomly allocated to receive either photon or proton therapy. Recruitment began in February 2016 and will continue through the end of 2021.