ESTRO 2025 - Abstract Book

S532

Clinical - Breast

ESTRO 2025

Results:

From February 2023 to September 2024, ten Luminal B BC patients, predominantly with cT2 tumors, were enrolled in the trial. The preoperative SBRT boost was scheduled between the 3rd and 4th paclitaxel administration. The SBRT treatments were delivered using the Volumetric Arc Modulated Therapy (VMAT) technique with flattening filter free and Deep Inspiration Breath Hold, ensuring optimal target coverage and minimal exposure to organs-at-risk (OaRs). The prescribed dose was 24 Gy in 3 fractions of 8 Gy each. A key focus was on sparing OaRs, especially the skin, to prevent surgical complications. In all cases, SBRT planning with VMAT was successfully implemented, maintaining a mean PTV/breast ratio of 5.3%. Only one patient required a reduction in CTV V95% below 98% to meet OaRs constraints. Importantly, no acute skin toxicities were observed (Table 1). Conclusion: The preliminary results of the IBISCO trial suggest that the integration of a preoperative SBRT boost with NAC is not only feasible but also safe for treating BC. This approach, using advanced RT techniques, has shown potential in delivering precise and effective treatment without significant acute skin toxicities. The final results of the study are awaited to confirm these initial observations and potentially influence treatment strategies for this specific BC subtype. Digital Poster Early changes in left ventricular function following adjuvant radiotherapy for breast cancer Felix Mehrhof 1 , Stephen Schueuerhuis 2 , Marcus Beck 1 , Sebastian Zschaeck 1 , Alexandra M Chitroceanu 3,4 , Daniel Zips 1 , Frank Edelmann 3,4 , Franziska Hausmann 1 1 Department for Radiation Oncology, Charité - University Medicine Berlin, Berlin, Germany. 2 Institute for Biometry and Clinical Epidemiology, Charité - University Medicine Berlin, Berlin, Germany. 3 Department of Cardiology, Angiology and Intensive Care Medicine, Deutsches Herzzentrum der Charité (DHZC), Berlin, Germany. 4 German Center for Cardiovascular Research, DZHK, Berlin, Germany Purpose/Objective: Adjuvant radiotherapy following breast-conserving surgery leads to exposure of the heart. Long term cardiotoxic effects of radiotherapy have been described especially for left sided breast cancer patients. We examined early changes of laboratory and echocardiographic parameters following intensity-modulated radiotherapy (IMRT) in a single institution. Keywords: preoperative SBRT, Luminal B, pCR 2428