Phase 3 trial of hypofractionated versus conventional fractionated postmastectomy radiotherapy for high-risk breast cancer: 10-year outcomes

Hypofractionated radiotherapy is an established alternative to conventional fractionation for breast cancer, but long-term evidence after mastectomy with regional nodal irradiation in scarce. The phase 3 CHN HYPOPMRT trial at the Chinese Academy of Medical Sciences and Peking Union Medical College (Beijing) compared postmastectomy conventional fractionated radiotherapy (50 Gy in 25 fractions over 5 weeks) versus hypofractionated radiotherapy (43 Gy in 15 fractions over 3 weeks) to the chest wall and supraclavicular region. Ten-year outcomes from the trial have now been published. A total of 810 patients were included in the analyses (409 conventional RT; 401 hypofractioned RT). Median follow-up was 11.5 years (IQR 9.6-13.8). At 10 years, cumulative locoregional recurrence was 10.3% (95% CI 7.3-13.3) with conventional fractionated RT and 12.0% (8.8-15.2) with hypofractionated RT (HR 1.19; 95% CI 0.79-1.82). The most common grade 3 adverse events at 10 years were ischemic heart disease (five patients in each group), lymphedema (four versus three patients), shoulder dysfunction (two versus one patients), and skin adverse events (none versus one). No grade 4 or 5 events occurred. The authors conclude that hypofractionated postmastectomy radiotherapy provided durable locoregional control with no increase in severe late adverse events compared with conventional fractionation, supporting its use as a more time-efficient option than conventional fractionated radiotherapy.