Effect of radiotherapy on coronary arteries and heart in breast-conserving surgery: a dosimetric analysis.

Background. There are certain risks of radiotherapy (RT), especially patients with left-sided breast cancer have a higher tendency to develop cardiac complications than the right-sided cancers. This study aims to perform a dosimetric analysis the effect of RT on coronary arteries and heart in breast-conserving surgery. Patients and methods. A total of 40 patients with early stage right and left-sided breast carcinomas (T1/T2 + NO) were randomly selected. RT was delivered to the entire breast, and tumor beds were boosted in these patients using tangential fields with computed tomography based planning. The doses for Left anterior descending coronary artery (LAD), left circumflex coronary artery (LCx), right ventricle (RV), left ventricle (LV), and heart were recorded and median values compared between groups. Results. The highest mean of radiation dose in patients with left-sided breast cancer was to LAD 2402.48 +/- 838.39 cGy, while the highest mean dose in right-sided breast cancer patients was to RV 130.18 +/- 24.92. The highest maximum dose of radiotherapy was applied to heart at left-sided breast cancer patients as well as at right-sides prients. The mean V5 of the LV was 18.68% (6.89-31.69), mean V25 of the LV was 5.22% (0.45-16.54), mean V5 in bilateral ventricles was 23.73% (2.56-26.89), and mean V25 in bilateral ventricles 6.78% (0.63-13.63). Conclusions. Especially in left-sided breast cancer, the most direct and best strategy to reduce and protect radiation-induced cardiac injury is to balance dose constraints between several high-dose regions of cardiac substructures and the mean heart dose.