S285
Clinical - Breast
ESTRO 2026
primary endpoint. Induration analyses started 2 years after surgery, and an event was defined as the first grade ≥ 2 induration that was also present at a subsequent visit or at the last visit. Overall survival, distant recurrence, and breast cancer–specific mortality were analysed using Kaplan–Meier, competing risks, and Cox models to estimate hazard ratios (HR). Results: Median follow-up was 12.77 years (95% CI 12.67– 12.91). Breast induration analyses included 1,843 patients. The cumulative incidence of induration at 5 and 10 years was 21.8% and 24.7% (50Gy/25fr), and 17.3% and 19.5% (40Gy/15fr); HR 0.76 (95% CI 0.62– 0.92; p = 0.005).In the survival analyses, 1,853 patients were included. The cumulative incidence of distant recurrence was 5.4%, 14.2% and 18,1% at 5,10 and 12 years for patients treated with 50Gy/25fr, and 4.5%, 11.8% and 15,1% for those treated with 40Gy/15fr. The HR was 0.81 (95% CI, 0.48–1.38; p = 0.44).Breast cancer–specific death occurred in 67 patients; the 10- year cumulative incidence was 2.7%. The HR for breast cancer–specific death for 40Gy/15fr compared with 50Gy/25fr was 0.65 (95% CI 0.39–1.05; p = 0.08).The 10- and 12-year overall survival rates were 92.1% and 88.0% (50Gy/25fr), and 93.0% and 90.5% (40Gy/15fr); HR for death 0.81 (95% CI 0.62–1.04; p = 0.10). Conclusion: At median follow-up of 12.8 years, 40Gy/15fr did not cause more 5- and 10-year breast induration, in fact, it led to a 24% reduced relative risk of induration. Furthermore, compared to 50Gy/25fr, patients treated with 40Gy/15fr had similar outcomes regarding distant failure, death from breast cancer and overall survival. These outcomes support the long-term safety profile of the hypofractionated regimen.
References: 1. Offersen B V, Alsner J, Nielsen HM, Jakobsen EH, Nielsen MH, Krause M, et al. Hypofractionated Versus Standard Fractionated Radiotherapy in Patients With Early Breast Cancer or Ductal Carcinoma In Situ in a Randomized Phase III Trial: The DBCG HYPO Trial. J Clin Oncol. 2020 Nov 1;38(31):3615–25. Keywords: Trial, Hypofractionated, whole breast Poster Discussion 2692 Real-World Evidence on Fractionation and Survival in Breast Cancer with an Indication for Nodal Irradiation Irina Surovtsova 1 , Markus Schirmer 2 , Philipp Morakis 2 1 Clinical State Registry Baden-Württemberg, Clinical State Registry Baden-Württemberg, Stuttgart, Germany. 2 Quality Conferences Office, Clinical State Registry Baden-Württemberg, Stuttgart, Germany Purpose/Objective: Hypofractionated radiotherapy (HFRT) is an established standard for breast cancer, offering comparable efficacy to conventional fractionation (CFRT) with improved convenience and lower toxicity. While well validated for whole-breast irradiation, its role in patients requiring regional nodal irradiation remains debated. Two recent randomized trials reported differing results regarding overall survival (OS): HypoG-01 suggested a potential advantage for HFRT in oncologic outcomes, whereas SKAGEN found
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