Ultra-hypofractionated versus hypofractionated radiotherapy in breast cancer: Real-world toxicity, efficiency, and implementation patterns.

Abstract

e12722 Background: Hypofractionated regimens are standard for breast-conserving therapy due to equivalent efficacy and reduced treatment burden. Ultra-hypofractionated regimens have demonstrated non-inferior outcomes in randomized trials; however, real-world data on safety, efficiency, and implementation remain limited, particularly in Latin America. Methods: We conducted a retrospective cohort study including patients with breast cancer treated with curative or adjuvant external beam radiotherapy at a comprehensive cancer center in Colombia. Patients received hypofractionated or ultra-hypofractionated regimens. Clinicopathological variables, treatment duration, and RT-associated toxicity were collected. Comparisons between regimens were performed using bivariate analyses. Results: A total of 121 patients were included, of whom 97 (80.1%) received hypofractionated and 24 (19.8%) ultra-hypofractionated radiotherapy. RT-related toxicity was infrequent and comparable between regimens (9.3% vs 4.2%), limited to skin toxicity. Ultra-hypofractionated RT was associated with a shorter treatment duration (5 vs 15 days). Ultra-hypofractionation was implemented across age groups, disease stages, and molecular subtypes, with no significant differences between regimens. A non-significant trend toward higher lobular histology was observed in the ultra-hypofractionated group. Three-year overall survival was high in both groups (98.9% vs 100%); survival analyses were descriptive due to a low number of events. Conclusions: Ultra-hypofractionated whole-breast radiotherapy demonstrated a safety profile comparable to hypofractionated regimens, with low rates of RT-related toxicity. Ultra-hypofractionation was implemented across a broad range of clinical characteristics, suggesting feasibility in routine practice. Survival outcomes were high in both groups and should be interpreted in the context of the limited number of events. These findings support ultra-hypofractionated radiotherapy as an efficient and safe strategy that may optimize quality of care and resource utilization in breast cancer. Baseline characteristics and outcomes by radiotherapy regimen. Variable Hypofractionated (n=97) Ultra-hypofractionated (n=24) Age, years 53.9 59.4 AJCC stage I–II, n (%) 76 (80.0) 19 (82.6) AJCC stage III, n (%) 18 (20.0) 4 (17.4) Invasive lobulillar carcinoma, n (%) 8 (8.2) 7 (29.2) Invasive ductal carcinoma, n (%) 79 (81.4) 14 (58.3) Any RT-related toxicity, n (%) 9 (9.3) 1 (4.2)