S252
Clinical - Breast
ESTRO 2026
reduced in ABC-DIBH group: Compared with FB, ABC- DIBH reduced the mean dose to the whole heart, LAD, LV and RV by 34% (2.70 vs. 4.09 Gy), 50% (4.85 vs. 9.68 Gy), 49% (2.63 vs. 5.14 Gy) and 45% (4.36 vs. 7.92 Gy), respectively (all p < 0.05*). Evaluated by CMR, no significant differences were observed in biventricular volumes, ejection fractions and myocardial mass in both two groups between pre- and post-radiotherapy (all p > 0.05). In FB group, the reductions were observed in LV Global Longitudinal Strain ( − 17.12 ± 2.00 vs. − 16.35 ± 2.23, p = 0.035*), LV Global Circumferential Strain ( − 20.75 ± 2.35 vs. − 19.94 ± 2.40, p = 0.020*) and RV-GLS [-17.37 (-21.51, -12.79) vs. − 14.40 ( − 20.65, − 9.69), p = 0.009*]. No such changes were noted in ABC-DIBH groups. Multivariate analysis showed changes of myocardial strain were exclusively associated with heart radiation dose. In the entire cohort, 5 patients in FB group developed mild asymptomatic cancer therapy-related cardiac dysfunction (CTRCD) after radiotherapy. Compared with the patients without CTRCD, They showed higher dose irradiation of whole heart (4.98 vs. 3.21 Gy), LAD (14.66 vs. 6.04 Gy), LV (6.86 vs. 2.96 Gy) and RV (10.28
Poster Discussion 1700
CMR analysis of acute cardiotoxicity after HFRT with SIB radiotherapy in breast cancer with or without active breathing coordinator:a randomized study Xinyu Lv 1 , Mengxi Yang 2 , Cheng Luo 3 , Linlin Zheng 1 , Hao Wang 4 , Jianhui Zhang 4 , Jinyi Lang 3 , Jun Yin 5,3 1 Department of Radiation Oncology, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China. 2 Department of Radiology, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, University of Electronic Science and Technology of China, Chengdu, China. 3 Department of Radiation Oncology, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, University of Electronic Science and Technology of China, Chengdu, China. 4 Department of Breast Surgery, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, University of Electronic Science and Technology of China, Chengdu, China. 5 Department of Clinical Oncology, Affiliated Hospital of Sichuan Nursing Vocational College, The Third People's Hospital of Sichuan Province, Chengdu, China Purpose/Objective: The active breathing coordinator with deep inspiration breath hold (ABC-DIBH) has demonstrated cardiac dosimetric benefits. However, it remains uncertain whether ABC-DIBH offers actual cardiac protection in hypofractionated radiotherapy with simultaneous integrated boost (HFRT with SIB). This study aims to prospectively evaluate the acute cardiac changes detected by cardiovascular magnetic resonance (CMR) after radiation for left-sided breast cancer with or Women diagnosed with left-sided breast cancer staged Tis-2N0M0 who receiving breast-conserving surgery (BCS) were recruited and randomly assigned to receive either ABC-DIBH or Free Breathing (FB). All the patients received HF whole breast irradiation (WBI) with SIB radiotherapy delivered by VMAT, which included WBI at 40.5 Gy/15Fx and a SIB at 48 Gy/15Fx. CMR was performed within 2 weeks before and after without ABC-DIBH. Material/Methods: RT to quantify left and right ventricular(LV/RV) conventional function and myocardial strain. Associations between CMR-measured changes and radiation dose were evaluated. Results: Between 2023 and 2025, 60 (32 ABC and 28 FB) patients were totally enrolled, and the two groups were well matched. Cardiac exposure was significantly
vs. 5.64 Gy) . Conclusion: In HF-WBI with SIB radiotherapy, ABC-DIBH
significantly reduces cardiac radiation exposure and prevents acute biventricular cardiac dysfunction in early left-sided breast cancer. References: 1.Coles CE, Haviland JS, Kirby AM, et al. Dose-escalated simultaneous integrated boost radiotherapy in early breast cancer (IMPORT HIGH): a multicentre, phase 3, non-inferiority, open-label, randomised controlled trial. Lancet. 2023; 401(10394):2124-2137. doi:10.1016/S0140-6736(23)00619-02.Lyon AR, López- Fernández T, Couch LS, et al. 2022 ESC Guidelines on cardio-oncology developed in collaboration with the European Hematology Association (EHA), the European Society for Therapeutic Radiology and Oncology (ESTRO) and the International Cardio- Oncology Society (IC-OS). Eur Heart J. 2022; 43(41):4229-4361. doi:10.1093/eurheartj/ehac244 Keywords: HFWBI-SIB; ABC-DIBH; CMR;
Digital Poster 1723
Optimizing planning procedures as preparation for ultra-hypofractionated partial breast irradiation: a reassessment of margins and dose constraints Kristian Boye, Marie Elgaard Korsholm Andersen, Marie Benzon Mogensen, Maja Vestmø Maraldo Department of Oncology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
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