Dosimetry study of fourtypes of radiotherapy plan optimization methods in the hypofractionated radiotherapy for lung cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective To discuss the dosimetric differences in the planning methods between physical and biological optimization during thehypofractionated radiotherapy for lung cancer.MethodsTen cases of non-small cell lung cancer (NSCLC) receiving radiotherapy were selected in this retrospective study.The VMAT plans for all patients were re-designed by physical functions (DV group),biological combined with physical functions (DV+EUD group and EUD+DV group) and biological functions (EUD group).The constrained functions were different,whereas the constrained conditions and optimized parameters were identical among four groups.The dosimetric differences among four optimization methods during thehypofractionated radiotherapy for lung cancer were evaluated through calculating and analyzing each dosimetry parameter.Results For the target area,the equivalent uniform dose was approximate between the EUD and EUD+DV groups.The EUD in these two groups was approximately 2.8％-3.6％ and 3.2％-3.7％ higher than those in the DV and DV+EUD groups.The average tumor control probability (TCP) in the EUD and EUD +DV groupswas considerably higher than those in the other two groups (both P＜0.05).The homogeneity index (HI) significantly differed (all P＜0.05),whereas the conformity index (CI) did not differ (all P＞0.05).For the organ at risk (OAR) area,the differences of EUD,V5,V1o,V20,V30 of normal lung tissues and the difference of dosimetry parameters in heart and spinal cord were not statistically significant (all P＞0.05).The mean dose of all lungs in the EUD and EUD+DV groupswas slightly lower than those in the other two groups.ConclusionsBiological optimization method has certain advantages in increasing EUD and TCP in the target area and decreasing the irradiation dose of normal lung tissues,which provides references for selecting the optimization method with biological functions in clinical practice.