Estimation of the effect of target and normal tissue sparing based on equivalent uniform dose-based optimization in hypofractionated radiotherapy for lung cancer*

Abstract

Abstract Objective This study aims to investigate the dosimetric differences among four planning methods of physical and biological optimization in hypofractionated radiation therapy for non-small cell lung cancer (NSCLC). Methods Ten NSCLC patients receiving radiation therapy were chosen for this retrospective study. Volumetric modulated arc treatment plans for each patient were remade with dose-volume (DV) functions, biological-physical functions, and biological functions, using the same constraint parameters during optimization. The dosimetric differences between the four types of plans were calculated and analyzed. Results For the target, equivalent uniform dose (EUD) of the EUD and EUD + DV groups was approximately 2.8%-3.6% and 3.2%-3.7% higher than those of the DV and DV + EUD groups, respectively. The average tumor control probability (TCP) of the EUD and EUD + DV groups was also significantly higher than those of the other two groups (P < 0.05). The difference in heterogeneity index (HI) among the four groups was also statistically significant (P < 0.05), while the difference of conformity index (CI) was not significant (P > 0.05). For the organs at risk, the differences of EUD, V5, V10, V20, V30 of normal lung tissues were not statistically significant (P > 0.05); however, the mean lung dose of the EUD and EUD + DV groups was slightly lower than those of the other two groups. Conclusion The biological optimization method has obvious advantages of improving EUD and TCP of the target, while decreasing the exposed dose of normal lung. This result is meaningful in choosing plan optimization methods in routine work.