S226
Clinical - Breast
ESTRO 2026
SABR stands as a highly effective, non-invasive alternative to surgery or exclusive hormone therapy in this selected patient cohort, warranting further investigation in phase II studies. References: Meattini I, Becherini C, Boersma L, et al. European Society for Radiotherapy and Oncology Advisory Committee in Radiation Oncology Practice consensus recommendations on patient selection and dose and fractionation for external beam radiotherapy in early breast cancer. Lancet Oncol. 2022 Jan;23(1):e21- e31Moore-Palhares D, Chen H, Khan BM, et al. Locoregional Ablative Radiation Therapy for Patients With Breast Cancer Unsuitable for Surgical Resection. Pract Radiat Oncol. 2024 Jul-Aug;14(4):316- 327.Zabrocka E, Roberson JD, Noldner C, et alA. Stereotactic body radiation therapy (SBRT) for the treatment of primary breast cancer in patients not undergoing surgery. Adv Med Sci. 2024 Mar;69(1):29- 35 Keywords: SABR, breast, inoperable Digital Poster Highlight 929 Subclinical atherosclerosis: Risk marker for post- radiotherapy breast edema? Ana A Diaz-Gavela 1,2 , Elia del Cerro Peñalver 1,2 , Felipe Counago 3 , Israel J Thussard-Vasallo 4 , Julio Fernandez- Mata 5,2 , David Sanz-Rosa 2 , Sofia Sanchez-Garcia 6 , Marina Pena-Huertas 1,2 , Victor Duque-Santana 1,2 , Luis L Guerrero 6 , Hugo Perez-Garcia 7 , Gines Hernandez- Cortes 8 , Cristina Andreu-Vazquez 9 1 Radiation Therapy Department, Quironsalud Madrid University Hospital, Pozuelo de Alarcon, Spain. 2 Department of Medicine, Fac. of Biomedical and Health Sciences, Universidad Europea de Madrid, Villaviciosa de Odón, Spain. 3 Radiation Therapy Department, La Milagrosa Hospital, Madrid, Spain. 4 School for Doctoral Studies and Research, Universidad Europea de Madrid, Villaviciosa de Odon, Spain. 5 Radiology Department, Quironsalud Madrid University Hospital, Pozuelo de Alarcon, Spain. 6 Radiation Therapy Department, Quironsalud La Luz Hospital, Madrid, Spain. 7 Radiophysics Department, Quironsalud Madrid University Hospital, Pozuelo de Alarcon, Spain. 8 Gynecology and Obstetrics Department, Quironsalud Madrid University Hospital, Pozuelo de Alarcon, Spain. 9 Veterinary Department, Universidad Europea de Madrid, Villaviciosa de Odon, Spain Purpose/Objective: Chronic breast edema is a relevant late sequela of adjuvant radiotherapy (aRT) for breast cancer (BC), with clinical impact on quality of life and oncological follow-up. Although its risk has traditionally been
tolerability, and maximum tolerated dose (MTD) of SABR as a definitive treatment in this population. Material/Methods: A single-center, single-arm, phase I study was designed. Eligible patients were ≥ 70 years old with unifocal, T1-2N0 M0-1 breast cancer, considered inoperable or who refused surgery. A Fibonacci (3+3) dose-escalation design was used to deliver SABR to the primary tumor in 5 fractions. Dose levels were 36 Gy (Level 1), 38 Gy (Level 2), and 40 Gy (Level 3). The primary endpoint was dose-limiting adverse effects, defined as any ≥ Grade 3 events (per RTOG/Harris scales) within the first 6 months. Secondary endpoints included local control (LC), progression-free survival (PFS), and overall survival (OS). Results: Between March 2021 and March 2024, 10 patients (11 tumors) with a median age of 91 years (range: 83-96) were enrolled. Three patients received 36 Gy, three received 38 Gy, and four received 40 Gy. With a median follow-up of 27 months (range: 4-40), no dose- limiting adverse events were observed in any cohort, and thus the MTD was not reached. No acute adverse events were recorded. The only late adverse effect reported was one case (10%) of Grade 1 subcutaneous fibrosis at 6 months in the 36 Gy level. Cosmetic outcome was excellent or good in 100% of patients. An overall response rate of 90% (40% complete response, 50% partial) was achieved. At 24 months, local control was 90%. Both 24-month PFS and OS were 90%.
Figure 2- SABR treatment Conclusion:
Definitive SABR for primary breast cancer in elderly and/or frail patients is an exceptionally safe and well- tolerated procedure up to a dose of 40 Gy in 5 fractions. Furthermore, it demonstrates promising preliminary efficacy with excellent disease control.
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