ESTRO 2025 - Abstract Book

S579

Clinical - Breast

ESTRO 2025

3497

Digital Poster Ultra-hypofractionated radiotherapy in breast cancer: analysing the relation between the dose to cardiac substructures and cardiac events. María Medina-Cobacho, Victoria Vera-Barragan, Esther Agudo-Rey, Patricia Ruiz-Leal, Camila Fernandez-Alcala, Yesika Rios-Kavadoy, Francisca Ropero-Carmona, Carmen Corral-Fernandez, Juan Quirós-Rivero Radiation Oncology, Hospital Universitario de Badajoz, Badajoz, Spain Purpose/Objective: Ultra-hypofractionated radiotherapy (UHR) is the new standard of care in early-stage breast cancer. A concern is the risk of increasing cardiotoxicity in the patients (1-2). Previous studies concluded that coronary arteries were better predictors of cardiac events and found that they received significant doses with radiotherapy treatment (3-4). A retrospective review was performed to analyze overall survival (OS), progression-free survival (PFS) and toxicity, with special interest in the correlation between mean dose to cardiac substructures and cardiac events, in women with early-stage breast cancer treated with UHR. Material/Methods: Women diagnosed with invasive carcinoma of the breast (pT1-pT2), treated with conservative surgery and adjuvant UHR (26 Gy in five consecutive fractions) between August 2019 and August 2022 were included. Data on previous history of cardiac disease or cardiovascular risk, systemic treatment, toxicities during and after treatment, cardiac events and cosmetic results was collected. Left anterior descending coronary artery (LAD), circumflex coronary artery (Cx), left main coronary artery (LMCA) and the heart were contoured to assess dose distribution in patients with left breast cancer. OS and DFS were analysed using Kaplan-Meier curves and the correlation between cardiac events and the mean dose to cardiac substructures using logistic regression analysis.

Results: A total of 151 patients with a median age of 68, 54.3% with left sided breast cancer, were collected. In left-sided treated patients, the mean dose to the heart was 1.66 Gy (0.87-3.48), to the LAD was 5.01 Gy (0.58 21.34), to the Cx was 0.96 Gy (0.67-1.33) and to the LMCA was 0.87 Gy (0.52-1.12). Only 2 patients from our cohort had cardiac events after treatment. No statistical correlation was found between the mean dose to the heart (p=0.18) or the coronary arteries (p= 0.19) and cardiac events. With a median follow-up of 60 months (59-61), PFS and OS were 98%. Most of the patients (78.8%), had no chronic toxicity and reported excellent cosmetic results (84.1%).