Randomized phase 2 trial of conventionally fractionated versus hypofractionated postmastectomy proton radiotherapy

Proton therapy is under investigation in breast cancer as a strategy to reduce radiation exposure to the heart and lungs. So far, studies investigating proton postmastectomy radiotherapy (PMRT) have used conventional fractionation over 25-28 days, but whether hypofractionated proton PMRT is feasible is unclear. The randomized phase 2 MC1631 study at two Mayo Clinics compared conventionally versus hypofractionated proton postmastectomy radiotherapy. After a median of 39.3 months, noninferiority of the hypofractionation group could not be established. However, given similar tolerability, the authors conclude that hypofractionated proton PMRT appears to be worthy of further study.