Pre-treatment predictors of cardiac dose exposure in left-sided breast cancer radiotherapy patients after breast conserving surgery

Objectives: This study aimed to identify high-risk factors for high cardiac radiation exposure, based on anatomical measurements taken from planning CT images of patients with left-sided breast cancer who underwent breastconserving surgery and received radiotherapy. Methods: We retrospectively analyzed 45 patients with left-sided breast cancer who underwent whole-breast radiotherapy, either under free breathing (27/45) or deep inspiratory breath- holding ( DIBH) (18/45), after breastconserving surgery. Six anatomical parameters were measured from planning CT images, including treatment planning target volume (PTV), cardiopulmonary volume ratio (CVR), maximum cardiac margin distance, the relative distance between inferior boundaries of heart and PTV (DBIB(H2P)), axial cardiac contact distance, and parasagittal cardiac contact distance (CCDps). Multiple linear regression analysis was performed using SPSS software to explore the correlation between the six parameters, body mass index (BMI), and the mean heart dose (MHD). Receiver operating characteristic ( ROC) analysis was performed to evaluate the predictive power of the selected predictor of cardiac dose exposure. Results: Significant correlations were observed between the MHD of patients and the CVR, DBIB(H2P), and CCDps parameters. Among them, the CVR was the most important predictor of cardiac dose exposure, with an area under the curve of 0.915 and a cut-off value of 0.17. Conclusions: The study results indicated that CVR, DBIB(H2P), and CCDps are the primary parameters associated with the risk of cardiac dose exposure, with CVR being the most significant predictor. Further prospective studies are required to determine whether these parameters can be used to identify patients who would benefit from the DIBH technique.