ESTRO 2025 - Abstract Book

S511

Clinical - Breast

ESTRO 2025

Results: A total of 50 patients were included. Radiotherapy wad delivered to the whole breast in 52% and to the chest wall in 48% of cases. Nodal irradiation was performed in 64% of patients, including axillary lymph nodes for 7 (14%) patients. Eighteen (36%) patients were planned for additional boost. The tumor bed was internal in 53.2% of cases. Compared with FB plans, CPAP plans yielded substantially lower doses to the heart, LV and LAD. The mean MHD was decreased by 43.8%: 4.63 Gy vs 2.6 Gy, p=0.00 (Table1). CPAP use was related to an absolute mean reduction of 8.74 Gy in Dmean LAD (range 4.6 to 12.8 Gy) and more than 65% of reduction in V26.5Gy and V35.3Gy LAD (all p =0.00). The V17Gy and V28.5 to ipsilateral lung were significantly lower in CPAP plans: 26.4% vs 23.9% (p=0.03) and 19% vs 16% (p=0.00), respectively. The CPAP benefit was significantly higher in RT plans requiring IMC irradiation with an average decrease of 55% for MHD, Dmean LAD and Dmean LV (p=0.00). Conclusion: CPAP use in left-sided breast cancer radiotherapy was related to substantial dose reduction to critical heart subvolumes. These data supports CPAP as an affordable and efficient heart sparing technique with low infrastructural requirement and easy implementation. Digital Poster FAST-Forward Radiotherapy with Simultaneous Integrated Boost and Nodal Irradiation in Early-Stage Breast Cancer: Safety and Outcomes Isabela Gaztelu 1 , Ines Ollinger 1 , Gema Muñiz 2 , Roberto De Haro 1 1 Radiation Oncology, Hospital Universitario Virgen del Rocio, Seville, Spain. 2 Medical Physics, Hospital Universitario Virgen del Rocio, Seville, Spain Purpose/Objective: To evaluate acute and late toxicities associated with the FAST-Forward radiotherapy regimen using Simultaneous Integrated Boost (SIB) and regional nodal irradiation (RNI) in early-stage breast cancer patients and examine potential correlations with patient characteristics and prior treatments. Material/Methods: This retrospective, observational study included 120 patients with early-stage breast cancer (pT1-3, pN0-1, M0) treated with surgery and adjuvant radiotherapy using the FAST-Forward protocol (5 daily fractions) between June 2021 and October 2023. SIB was applied to the tumor bed in 90% of patients undergoing breast-conserving surgery, while RNI Keywords: CPAP; heart sparing; breast radiotherapy 2135