Divided target optimization with volumetric modulated arc therapy planning to improve target coverage and homogeneity in lung radiation therapy

Purpose: To investigate and evaluate the feasibility of a simple modified Divided Planning Target Volume (DPTV) optimization method in radiation therapy planning of lung cancer patients. Methods: A cohort of 15 patients of Non-Small Cell Lung Cancer (13 patients stage III and two patients of stage II) who were previously treated with Concurrent Chemo Radiation Therapy were included in the study. The planning modality was Volumetric Modulated Arc Therapy, and the dose prescription was 60 Gray in 30 fractions. In this study, we attempted to replan by dividing the previous Single Planning Target Volume (SPTV) into a DPTV. All the treatment plans were re-vised and again optimized for DPTV with required dose constraints as in SPTV. The dosimetric parameters that were achieved for target and normal structures were recorded in both the optimization methods. Results: Dosimetric target coverage (D95%) (p-value = 0.0001), dose homogeneity (p-value = 0.0001) and conformity (p-value = 0.044) were improved by the DPTV optimization. The volume of the oesophagus receiving 35 Gy was found to be higher in the DPTV arm (p-value = 0.02) compared to the SPTV arm, but the volume of the oesophagus receiving 50 Gy was found to be similar (p-value = 0.122). Conclusion: In radiation therapy planning of lung cancer, the DPTV optimization method has better dose coverage to the target volume, homogeneity, as well as conformity than the stsndsrd SPTV method. Therefore, the DPTV optimization method can be a simple and efficient alternative to the SPTV method in lung cancer.