Atrial Fibrillation and Other Cardiac Arrhythmias and Diseases After Radiotherapy for Breast Cancer : Watch Your HeaRT

The goal of this interventional study is to evaluate the risk of atrial fibrillation (AF) and other cardiac arrhythmias and diseases in breast cancer patients treated with radiation therapy (RT). In addition to regular follow-up of patients by the radiation oncologist for 5 years, cardiovascular screening at the end of follow-up, combining the use of a connected watch and a cardiological check-up, could make it possible to identify precisely the types and frequencies of these sometimes asymptomatic, and probably underestimated, cardiac diseases. The main questions it aims to answer are: * To assess the incidence of AF and other cardiac arrhythmias and diseases occurring within 5 years after RT * To evaluate absorbed doses in the heart and cardiac substructures (chambers, conduction nodes, coronaries, pulmonary veins) based on auto-segmentation models developped with deep learning algorithms * To investigate whether the risk of AF and other cardiac arrhythmias and diseases is associated with cardiac irradiation characterized by these absorbed doses (dose-response relationship) Participants will be included between 2023 and 2025, 5 years after their RT: * Retrospective data collection will be based on a medical questionnaire designed to identify cardiac pathologies present prior to RT and those having occured in the past, between RT and 5 years post-RT. * Cross-sectional data collection will be based on screening for cardiac pathologies using a connected watch worn for 1 month (silent AF screening) and a cardiology consultation (including ECG and echocardiography) to identify cardiac pathologies at 5 years post-RT possibly not identified in the retrospective data collection.