Deep Inspiratory Breath-Hold Technique for Patients with Left-Sided Breast Cancer: Dosimetric Analysis, Clinical Evaluation, and Prediction

IntroductionBreast radiotherapy is associated with a higher risk of cardiac diseases. Although deep inspiration breath-hold (DIBH) reduces the heart dose, it is underutilized. The selection of proper candidates for DIBH remains an unresolved issue. This study compared dosimetric parameters between free breathing (FB) and DIBH, monitored myocardial enzymes, and aimed to identify factors that can predict cardiac injury thus developing a method to identify proper patients for DIBH.MethodsThis is a prospective cohort study, enrolling 58 patients with left-sided breast cancer following breast-conserving surgery. All patients underwent computed tomography scans in both FB and DIBH states. A comparative analysis of dosimetric features between DIBH and FB was conducted. Myocardial enzyme was monitored until six months post-radiation therapy. T-tests were used to assess differences between the DIBH and the FB. Pearson correlation and receiver operating characteristic (ROC) analysis was conducted to identify factors associated with the subclinical acute cardiac injury.ResultsThe mean heart dose (MHD) of the DIBH group significantly dropped as compared to the FB group (3.81 Gy vs 1.65 Gy p = 0.001). Cardiac V40, V30, V25, V10, and V5 volumes also significantly reduced. 9(15.51%) patients exhibited increased myocardial enzyme, with cTnI being the most sensitive indicator. The heart dose was a predictor for the cardiac enzyme's elevation. The ROC curve analysis revealed an area under the curve of 0.6. With an MHD threshold of 2 Gy, both sensitivity and specificity exceeded 0.7.ConclusionDIBH significantly diminishes radiation exposure to the heart and LAD compared with FB. Cardiac enzyme analysis facilitates the early detection of cardiac injury following radiation therapy. An MHD threshold of less than 2 Gy is associated with a reduced risk of subclinical cardiac injury, potentially obviating the need for DIBH, which optimizes clinical efficiency and economic viability.