{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T05:04:40Z","timestamp":1789535080365,"version":"build-2803163510"},"reference-count":23,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T00:00:00Z","timestamp":1789516800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008238","name":"Hebei Provincial Department of Science and Technology","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100008238","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Oncol."],"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To investigate dosimetric exposure variations to the whole heart and substructures between left- and right-sided breast cancer patients receiving intensity-modulated radiotherapy (IMRT), and to evaluate their relationships with post-radiotherapy (post-RT) electrocardiogram (ECG) alterations.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      Clinical and dosimetric data of 91 breast cancer patients (54 left-sided, 37 right-sided) undergoing postoperative free-breathing IMRT were retrospectively analyzed. Twelve-lead ECGs were regularly monitored during follow-up. Kaplan-Meier analysis evaluated ECG abnormality-free survival. Receiver operating characteristic (ROC) curves compared the predictive values of mean heart dose (MHD) and left ventricular mean dose (LV\n                      <jats:italic>D<\/jats:italic>\n                      <jats:sub>mean<\/jats:sub>\n                      ) for new-onset repolarization abnormalities in left-sided patients, utilizing mathematically derived population-specific split-points.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Target volume configurations (comprehensive regional and internal mammary node irradiation) drove distinct substructure exposure patterns between sides. In left-sided patients, MHD, LV, and left anterior descending artery (LAD) doses were significantly higher than those in right-sided patients (all\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0&amp;lt;\u00a00.001). Conversely, right-sided patients sustained significantly higher doses to the sinoatrial node (SAN) and right coronary artery (RCA) (all\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0&amp;lt;\u00a00.001). Left-sided patients had a significantly shorter median ECG abnormality-free survival than right-sided patients (7.0 vs. 12.0 months,\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0=\u00a00.038). Among the 60 patients developing post-RT ECG modifications (incidence: 81.5% in left-sided cases), left-sided cases predominantly exhibited repolarization abnormalities (68.2%), whereas right-sided cases primarily presented rhythm abnormalities (62.5%,\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0=\u00a00.032). In the left-sided subgroup, LV dosimetric parameters (LV\n                      <jats:italic>D<\/jats:italic>\n                      <jats:sub>mean<\/jats:sub>\n                      , LV\n                      <jats:italic>V<\/jats:italic>\n                      <jats:sub>5<\/jats:sub>\n                      \u2013\n                      <jats:italic>V<\/jats:italic>\n                      <jats:sub>80<\/jats:sub>\n                      ) were significantly higher in the repolarization group than in the rhythm group (all\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0&amp;lt;\u00a00.01). ROC analysis indicated that LV\n                      <jats:italic>D<\/jats:italic>\n                      <jats:sub>mean<\/jats:sub>\n                      outperformed MHD in predicting early repolarization changes (AUC: 0.776 vs. 0.715).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Early post-RT cardiotoxicity follows a laterality-specific \u201cdual-mechanism model.\u201d Left-sided modifications manifest primarily as acute\/subacute repolarization surrogates driven by diffuse LV exposure, whereas right-sided modifications present as rhythm-based stress from focal SAN exposure.<\/jats:p>\n                  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