ESTRO 2025 - Abstract Book

S507

Clinical - Breast

ESTRO 2025

dampening (BSRD). Treatment planning incorporated 4DCT, MRI for tumour size evaluation, and dose planning was performed with Pinnacle software.

Results: The median age of the patients was 86 years (range 64–93). Of the 14 patients recruited, only 7 received treatment. Among those who did not undergo treatment, one patient could not tolerate it, two declined treatment, and five opted for an alternative treatment regimen. Of the 7 patients who did receive treatment, 43% were in Stage I, 43% in Stage IIA, and 14% in Stage IIB. The most common molecular subtype was Luminal A (4/7), followed by Luminal B (2/7) and HER2-positive (1/7). Among treated patients, 4 out of 7 did not receive neoadjuvant therapy, while 1 received chemotherapy and 2 received a combination of chemotherapy and hormone therapy. In terms of adjuvant treatment, only one patient who had not undergone neoadjuvant treatment received hormone therapy subsequently, while the others continued with their previous treatment regimen. No patients experienced acute toxicity during treatment or in follow-up consultations. At the 6-month follow-up MRI, 1 patient showed stable disease, 3 showed a partial response, and 2 achieved a complete response. Conclusion: SBRT shows promise as a safe and effective treatment for inoperable breast cancer, particularly in early-stage and hormone-sensitive subtypes, with no acute toxicities observed. However, challenges in patient recruitment, eligibility, and the small sample size limit the applicability of findings. Further large-scale studies are essential to confirm the safety and efficacy of SBRT, especially for older populations and those with comorbidities, to establish its role as a primary treatment option. Digital Poster Local management of second breast cancer event after primary breast conserving therapy : the patient’s perspective Jean-Michel Hannoun-Levi 1 , Julie Margenthaler 2 , Youssef Zeidan 3 , Rosa Di Micco 4 , Isabel Rubio 5 , Jessica Gahm 6 , Bethany Anderson 7 , Frederick Dirbas 8 1 Radiation Oncology, Antoine Lacassagne Cancer Center, University of Cote d'Azur, Nice, France. 2 Surgical Oncology, Washington University, Washington, USA. 3 Radiation Oncology, Baptist Health South Florida, Boca Raton, USA. 4 Breast Surgery, IRCCS Ospedale San Raffaele Vita-Salute San Raffaele University, Milano, Italy. 5 Breast Surgical Oncology, Clinica Universidad de Navarra, Madrid, Spain. 6 Molecular Medicine and Surgery, Karolinska University Hospital, Stockholm, Sweden. 7 Radiation Oncology, University of Wisconsin, Madison, USA. 8 Surgery, Stanford University School of Medicine, Stanford, USA Purpose/Objective: In case of a second ipsilateral breast cancer event (2 nd iBCE) after primary breast conserving treatment (BCT), most patients are offered salvage mastectomy (SM). However, retrospective and prospective data propose 2 nd BCT with breast re-irradiation for selected patients. To guide the patient about the choice between SM and 2 nd BCT, she needs full information in order to decide on the “best” treatment for herself. An international survey dedicated to breast cancer patients was conducted to analyze patients’ preference and expectations. Material/Methods: In January 24, a survey was drafted jointly with breast cancer patient advocates from the US (n=6) and Europe (n=2). In June 24, the survey was validated with 33 questions divided into four themes: demographic data (n=10), oncological outcomes (n=10), patient views (n=10), and financial issues (n=3). Non-demographic questions were Keywords: SBRT, Inoperable breast cancer, Efficacy 2092