Feasibility of Dose Reduction to the Left Anterior Descending Coronary Artery without Compromising Target Volume Coverage Using Tomotherapy Techniques

Background: Radiotherapy is associated with a high risk of heart disease in patients with left-sided breast cancer. Previously, the entire heart was considered an organ at risk (OAR) during planning. Studies have shown that the effect of radiation therapy depends on the dose to specific heart substructures. However, the tolerance dose of the left anterior descending coronary artery (LAD), an important cardiac substructure, is yet to be determined. This study aims to verify the feasibility of reducing the LAD dose with appropriate dose-volume constraints for patients undergoing left whole-breast radiotherapy, without compromising the target dose coverage, using tomotherapy techniques.Method: This retrospective study generated tomohelical and tomodirect plans initially without considering the LAD as OAR in the treatment planning. To reduce the LAD dose, plans were regenerated by including the LAD as an OAR with appropriate dose constraints. The dose-volume histogram parameters of these plans were compared with those of the initial plans of the respective types.Results: Tomohelical plans showed a ۴.۴% reduction in maximum dose and a ۳.۸% reduction in V۱۵ for LAD, while tomodirect plans registered a ۳% reduction in V۱۵, with the conformity index remaining constant. Based on the LAD dosimetric results, considering the LAD as an OAR is associated with lower LAD doses without compromising the target volume coverage.Conclusion: It is feasible to reduce the LAD dose without compromising target volume coverage or affecting other OAR doses in patients with left breast cancer, using tomotherapy techniques.