Dosimetric evaluation of adding left ventricle and left anterior descending coronary artery cardiac substructures to plan optimization in left lung cancer radiotherapy

The impact of doses on the left ventricle (LV) and left anterior descending artery (LAD) in relation to major adverse cardiac events is well documented. Studies performed on breast cancer have shown that LV doses are correlated with cardiac toxicity.

Thirty-two patients with left lung cancer who received radiotherapy at our center were evaluated retrospectively. The left ventricle (LV) and left anterior descending artery (LAD) were contoured as organs at risk on CT simulation images. Seven fields were used in intensity-modulated radiation therapy (IMRT) plans, while two partial arcs were used to create volumetric modulated arc therapy (VMAT) plans. Conventional plans were compared with LV and LAD sparing plans dosimetrically.

When comparing conventional plans to sparing plans, no statistically significant differences were found in target volume parameters and values related to critical structures (p>0.05). However, when evaluating the heart (Dmean and V25) and its substructures (LADmean, V15, V30, and LV V5, V10, V15, V30, V40), the plan with LV and LAD sparing demonstrated significantly better outcomes (p<0.05).

Therefore, it is essential to contour the substructures of the heart as organs at risk, particularly including LAD and LV in the optimization algorithm during radiotherapy planning for central lung tumors located near the heart.