Wang SL, et al. - Researchers investigated the relative efficacy and safety of a 3-week schedule of postmastectomy hypofractionated radiotherapy vs a 5-week schedule of conventional fractionated radiotherapy. Outcomes revealed postmastectomy hypofractionated radiotherapy vs conventional fractionated radiotherapy was non-inferior in patients with high-risk breast cancer; the two treatment regimens also had similar toxicities. They identified hypofractionated radiotherapy to have potential in providing more convenient treatment and permits providers to treat more patients.

Methods

• Researchers conducted a randomized, non-inferiority, open-label, phase 3 study in a single academic hospital in China.
• Participants were patients aged 18–75 years who had undergone mastectomy and had at least four positive axillary lymph nodes or primary tumor stage T3–4 disease.
• Based on a computer-generated central randomization schedule, they randomized patients (1:1), without stratification, to receive chest wall and nodal irradiation at a dose of 50 Gy in 25 fractions over 5 weeks (conventional fractionated radiotherapy) or 43.5 Gy in 15 fractions over 3 weeks (hypofractionated radiotherapy).
• They performed primary and safety analyses using the modified intention-to-treat population (including all eligible patients who underwent randomization but excluding those who were considered ineligible or withdrew consent after randomization).
• Five-year locoregional recurrence was the primary endpoint; non-inferiority was established using a 5% margin (equivalent to a hazard ratio <1.883).

Results

• Researchers enrolled 820 patients and randomly assigned them to the conventional fractionated radiotherapy group (n=414) or hypofractionated radiotherapy group (n=406) between June 12, 2008 and June 16, 2016.
• The modified intention-to-treat analyses included 409 participants in the conventional fractionated radiotherapy group and 401 participants in the hypofractionated radiotherapy group.
• Locoregional recurrence developed in 60 (7%) patients at a median follow-up of 58.5 months (IQR 39.2–81.8) (31 patients in the hypofractionated radiotherapy group and 29 in the conventional fractionated radiotherapy group); the hypofractionated radiotherapy group and the conventional fractionated radiotherapy group had the 5-year cumulative incidence of locoregional recurrence of 8.3% (90% CI 5.8–10.7) and 8.1% (90% CI 5.4–10.6), respectively (absolute difference 0.2%, 90% CI −3.0 to 2.6; hazard ratio 1.10, 90% CI 0.72 to 1.69; p < 0.0001 for non-inferiority).
• The groups displayed no significant differences in acute and late toxicities, except that fewer patients in the hypofractionated radiotherapy group had grade 3 acute skin toxicity than in the conventional fractionated radiotherapy group (14 [3%] of 401 patients vs 32 [8%] of 409 patients; p < 0.0001).