Key clinical point: In patients with breast cancer (BC), hypofractionated proton postmastectomy radiotherapy (PMRT), which is administered in larger doses and fewer sessions, showed similar rates of complications as conventional fractionated proton PMRT.
Major finding: At a median follow-up of 39.3 months, both conventional fractionated and hypofractionated proton PMRT had similar complication rates (15% vs 20%; absolute difference 4.9%; one-sided 95% CI 18.5; P = .27), with all complications occurring in patients with immediate expander or implant-based reconstruction.
Study details: Findings are from the phase 2 MC1631 trial including 82 patients with BC who underwent mastectomy with or without immediate breast reconstruction and were randomly assigned to receive either conventional fractionated (50 Gy in 25 fractions of 2 Gy) or hypofractionated (40.05 Gy in 15 fractions of 2.67 Gy) proton PMRT.
Disclosures: This study was partly supported by Mayo Clinic and other sources. The lead author declared serving as co-chair of the Breast Cancer Subcommittee of the Particle Therapy Cooperative Group.
Source: Mutter RW et al. Conventional versus hypofractionated postmastectomy proton radiotherapy in the USA (MC1631): A randomised phase 2 trial. Lancet Oncol. 2023 24(10):1083-1093 (Sep 8). doi: 10.1016/S1470-2045(23)00388-1