Proton Radiation for Stage II/III Breast Cancer

The proposed Phase II study is seeking to build clinical data as a continuation of the original dosimetric analysis published by Ares et al. performed at Paul-Scherrer Institute (PSI). That comparison demonstrated a benefit form proton planning for patients with non-metastatic breast cancer requiring complex, loco-regional, postoperative radiotherapy.1 The advantages of PT were improved target coverage compared to standard photon irradiation and reduced dose to heart, lungs and contralateral breast. The study goal is to demonstrate a "meaningful benefit" of proton therapy for women with loco-regionally advanced breast cancer. The main clinical endpoints of this trial are the reduction of cardiac morbidity and mortality (coronary artery disease, myocardial infarction, cardiac insufficiency) and the reduction of contralateral, second breast cancer. Both adverse events are presently associated with external beam photon therapy. Both goals require longitudinal follow-up of minimum 5-10 years. Despite the logistical challenges of long term follow-up, the effort is needed in view of the compelling preclinical evidence of dose avoidance or even absence of radiation dose to heart and contralateral breast uniquely accomplishable by protons only.