Dose-related cardiac side effects and its impact on survival following thoracic radiotherapy: A scoping review

Radiation dose to the heart is associated with various cardiac side effects. However, the specific cardiac and pulmonary structures that contribute to these toxicities remain incompletely understood. Moreover, although multiple factors contribute to reduced survival after radiotherapy, the role of radiation-induced cardiac toxicity remains underrecognized. This scoping review aimed to evaluate the associations between radiation dose to specific cardiac and pulmonary structures, cardiac side effects, and survival. A total of 137 clinical studies were analysed in accordance with the PRISMA guidelines. Associations between radiation dose and cardiac side effects were identified not only for the whole heart but also for specific cardiac substructures, including myocardial segments, coronary arteries, and the pericardium. Notably, radiation dose to the lungs was also associated with decline in cardiac function, suggesting that minimizing cardiac toxicity may require consideration of both local cardiac irradiation and non-local irradiation of adjacent organs, particularly the lungs. Direct evidence linking cardiac side effects to survival was limited. Nevertheless, the observed associations between higher radiation doses, increased cardiac toxicity, and poorer survival suggest a potential relationship that warrants further investigation. These findings support the hypothesis that reducing specific cardiac side effects may benefit from targeted sparing of the relevant cardiac and pulmonary substructures. While many radiation-related cardiac side effects are now recognized, further research is needed to identify and characterize previously unrecognized manifestations and to clarify their contribution to long-term survival.