ESTRO 2025 - Abstract Book

S436

Clinical - Breast

ESTRO 2025

with any patient or treatment characteristics. However, IMN irradiation was significantly associated with a higher difference in mean heart dose (FB-DIBH; 0.36), p=0223).

Conclusion: DIBH in radiotherapy for right-sided breast cancer with regional lymph node involvement offers dosimetric benefits, reducing radiation exposure to the heart, lungs, and liver. These advantages make DIBH the preferred technique for treating right-sided breast cancer with nodal irradiation, especially when targeting the ipsilateral IMNs.

Keywords: Right breast Cancer, Deep inspiratory breathing

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Digital Poster Heart of the Matter: Cardiac Risk and Breast Radiotherapy - What's the Truth?

Virginia Garcia Reglero 1 , Sara Vazquez Gonzalez 1 , Luis Ramos Garcia 2 , Priscila Bernard Contreras 1 , Lucia Tueros Farfan 1 , Manuela Bermudez Zubiria 1 , Jose David Gonzalez Gomez 1 , Jose Enrique Baquedano Baquedano 1 , Marta Bonet Beltran 1 , Elena Garcia Alonso 1 , Moises Mira Flores 1 1 Radiation Oncology, Hospital Arnau de Vilanova, LLeida, Spain. 2 Radiophysics, Hospital Arnau de Vilanova, LLeida, Spain Purpose/Objective: Cardiac event (CE) remains a significant concern in patients with left-sided breast cancer undergoing radiotherapy. This prospective study investigated the prevalence of this complication in 1039 patients who received hypofractionated breast radiotherapy (40.05 Gy in 15 fractions) since 2016. Determine the incidence of long-term CE in breast cancer (BC) patients treated with radiotherapy, with a focus on identifying the timing and severity of this complication. Compare the incidence of CE between patients with left and right BC, excluding those who underwent deep inspiration breath hold during treatment. Identify patient characteristics and treatment factors that increase the risk of CE. Material/Methods: A prospective cohort study was initiated in 2016 to investigate the long-term outcomes of 1039 BC patients who underwent moderate hypofractionated radiotherapy. Patient characteristics, tumor details, systemic treatments, pre-existing comorbidities, and cardiac event occurrence were collected to identify predictors of cardiac even Statistical analyses were conducted to evaluate the incidence of CE, which were monitored through regular follow up assessments and medical record reviews. Results: The overall long-term incidence of CE in the study population was 2% (95% CI: 0.9-1.1). Patients who experienced CE had a median age of 67 years (51-83) while those without had a median age of 59 years (22-89). The median time to the onset of CE was 2.7 years. 34.7% of our patients received chemotherapy treatment, compared to 65.3% who did not. Both groups showed a similar incidence of CE. Odds ratio 0.8 (95% CI: 0.35-1.94) Among patients who suffered a CE, the distribution of BC laterality was relatively equal, with 48% presenting with right-sided disease and 52% with left-sided disease. There was no significant difference in the incidence of CE between patients with left-sided and right-sided BC Odds ratio 0,7 (0,307-1,63)