Purpose: To provide a dosimetric comparison among NSCLC treatment plans to determine whether minimizing dose to the left ventricle (LV) will significantly increase the dose to other organs at risk, while maintaining target coverage.
Methods: Fifteen Stage III non-small cell lung cancer (NSCLC) patients who have received a standard 60Gy in 30 fraction volumetric-modulated arc therapy (VMAT) treatment and with a V20Gy =20-30% were retrospectively replanned. The LV and left anterior descending artery (LAD) were additionally contoured on the end inhale and end exhale CT scans extracted from the clinical 4D-CT dataset and registered to the untagged average CT dataset that contained clinically defined targets and normal structures. The clinical treatment plans were retrospectively optimized with the goal of minimizing the mean(LV), and mean(heart) dose while maintaining the dose constraint of V20GyTotal Lung ≤30% and V95%PTV ≥95%. Dose-volume histograms and paired T-tests were used to compare the heart and lung dosimetric parameters, including mean heart, LV, and LAD doses, V5GyHeart , mean lung, V5GyLung and V20GyLung between the original and optimized treatment plans.
Results: Significant reduction (p≤0.044) were observed in mean(LV), mean(heart), mean(LAD), max(LAD) dose and V5GyHeart in the re-optimized treatment plans compared to the clinically delivered plans. V20GyLung ≤30% and V95%PTV ≥95% were maintained and insignificant differences were determined for parameters of mean(Lung), V5GyLung and V20GyLung, mean(esophagus) and mean(cord).
Conclusion: This study demonstrated that minimizing left ventricle dose in NSCLC treatment plans were achievable and dosimetrically advantageous in the heart while maintain dose constraints to normal lung and maximizing tumor control. Radiation dose reduction to cardiac substructures such as the left ventricle and LAD may decrease the risk of radiation-induced cardiac toxicity in this patient population.