New 10-year data from the CHN HYPOPMRT trial support the use of hypofractionated postmastectomy radiotherapy in high-risk breast cancer. The phase III study, presented at the ASTRO annual meeting and published in Lancet Oncology, compared a 3-week schedule (43.5 Gy in 15 fractions) with a conventional 5-week schedule (50 Gy in 25 fractions) in 820 patients with at least four positive axillary nodes or T3-4 disease.
At a median follow-up of 11.5 years, the cumulative locoregional recurrence rate was 12% in the hypofractionated arm versus 10.3% in the conventional arm (HR 1.19, 95% CI 0.79-1.82). Disease-free survival and overall survival were numerically higher in the hypofractionated arm, though the differences were not statistically significant. The authors concluded that the shorter regimen does not compromise long-term disease control or survival.
Safety outcomes were largely similar, with rare grade 3 adverse events and no brachial plexopathy or treatment-related deaths. However, grade 1 lung fibrosis was more common with hypofractionation (20% vs 12%). Discussant Janice A. Lyons noted that the trial, along with HypoG-01 and Skagen trial 1, supports a 3-week schedule, but she highlighted the underrepresentation of T4 and inflammatory breast cancer, calling for more research on dose escalation and tumor sensitivity.