Impact of hypofractionated radiotherapy schedules on local control in early breast cancer: A five-year study of boost vs. non-boost protocols

Abstract

Background: Hypofractionated radiotherapy (HFRT) is a standard treatment following breast-conserving surgery (BCS) for early breast cancer, yet the role of a tumor bed boost in HFRT protocols remains underexplored, particularly in resource-limited settings. This study evaluates the impact of boost versus non-boost HFRT schedules on local control in an Iranian cohort. Methods: In this retrospective cohort study, 270 women with early breast cancer (T1-T2, N0-N1, M0) treated with BCS and HFRT at Omid Hospital, Isfahan, Iran (2018-2019), were stratified into three groups (n = 90 each): Group A (40 Gy/15 fractions, 2.67 Gy/fraction), Group B (42.7 Gy/16 fractions, 2.67 Gy/fraction), and Group C (50 Gy total: 40 Gy/15 fractions + 10 Gy boost/5-6 fractions, 1.8 Gy/fraction). The primary endpoint was fiveyear local recurrence (LR), assessed via Kaplan-Meier estimates and Cox regression, adjusting for age, tumor size, stage, nodal status, and receptor status. Results: Over a median follow-up of 60 months, the overall LR rate was 10.0 (27/270). Group-specific rates were 10.0 (Group A), 13.3 (Group B), and 6.6 (Group C). A trend toward reduced LR with the boost was observed (HR 0.64, 95 CI 0.23-1.79, p = 0.396), though differences were not statistically significant (log-rank p = 0.29). Larger tumor size trended toward higher LR (p = 0.07). Conclusion: Adding a tumor bed boost to moderate HFRT may enhance local control in settings where ultrahypofractionation is impractical, warranting prospective validation in diverse populations.