ESTRO 2025 - Abstract Book

S567

Clinical - Breast

ESTRO 2025

3296

Digital Poster Hypofractionated vs. conventional radiation therapy for BRCA carriers with breast cancer Tali Orion 1 , Shir Schlosser 2,3 , Svetlana Zalmanov 1,4 , Raphael Pfeffer 1,4 , Ella Tepper 1,4 , Hana Lotan 1,4 , Vladislav Grinberg 1,4 , Julia Grinberg 1,4 , Irina Jiveliouk 1,4 , Roxolyana Abdah-Bortnyak 5,6 , Karen Drumea 7 , Yonina Tova 8 , Keren Hod 9 , Merav Akiva Ben David 1,4 1 Faculty of Health Science, Soroka University Medical Center, Ben Gurion University of the Negev, Beer Sheva, Israel. 2 Davidoff Cancer Center, Rabin Medical Center-Beilinson Hospital, Petah Tikva, Israel. 3 Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. 4 Department of Oncology, Assuta Medical Center, Tel Aviv, Israel. 5 Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel. 6 The Joseph Fishman Oncology Center, Rambam Health Care Campus, Haifa, Israel. 7 Department of Oncology, Carmel Medical Center, Haifa, Israel. 8 Department of Radiotherapy, Ziv Medical Center, Zefat, Israel. 9 Department of Academy and Research, Assuta Medical Center, Tel Aviv, Israel Purpose/Objective: Radiation therapy (RT) is a central treatment component in breast cancer (BC) management (1). Hypofractionated RT (HRT) has become increasingly favored over conventional RT (CRT) due to its comparable efficacy and reduced treatment duration (2). This study aims to compare the two protocols in terms of local recurrence for BRCA carriers with BC treated with breast conservation and radiation (BCT). Material/Methods: This is an IRB approved retrospective cohort of 387 BRCA1/2 carriers treated for BC at Assuta Medical Centers between 2013–2023. Patients who underwent BCT with minimal 24 months follow-up were included in this study. Two hundred patients, with 232 treated breasts were eligible and their medical records were reviewed. HRT was used for breast radiation only and for women older than 60 until 2019. Results: Mean follow-up time was 9.51 years (median 6.5 years, range 24-400 months, some had previous BC). Mean age at diagnosis was 53.2 in the HRT and 44.9 in the CRT (p<0.001). One hundred twenty-three (53%) of the breasts received HRT, with 84% tumor bed boost delivered, while only 74% in the CRT received a boost (p<0.001). Over half (54%) of the HRT were stage I, compared to 28% in CRT (p<0.01). BRCA1, BRCA2 and BRCA1+2 carriers were similar between the protocols with ~68%, 30% and 2%, respectively. Triple negative tumors were 50% and 51%, HER2 positive in 19% and 10%, and ER positive in 35% and 24% for HRT and CRT, chemotherapy was given to 67% and 79% (p<0.05), respectively. The five-year local recurrence was 1.62% and 0.09% in the HRT and the CRT (p=0.1) with no significant difference between mutations. With five years follow-up, 86.5% were free of disease, 10% developed metastatic disease and 5.5% died due to BC. In both groups, carriers diagnosed under the age of 40 were at higher risk of contralateral disease (HR=2.4, 95% CI 1.22-4.69). Conclusion: Excellent local control was demonstrated in this unique group of BRCA carriers, treated with BCT. Although small, the current data support the use of HRT in breast cancer patients and specifically presents the non-inferiority of the protocol compared to CRT in BRCA carrier patients.

Keywords: Short radiation protocol, local recurrence, BRCA

References: 1. Shah C, Bauer-Nilsen K, McNulty RH, Vicini F. Novel radiation therapy approaches for breast cancer treatment. Vol. 47, Seminars in Oncology. W.B. Saunders; 2020. p. 209–16. 2. Marta GN, Riera R, Pacheco RL, Cabrera Martimbianco AL, Meattini I, Kaidar-Person O, et al. Moderately hypofractionated post-operative radiation therapy for breast cancer: Systematic review and meta-analysis of randomized clinical trials. Breast. 2022 Apr 1; 62:84–92.