Impacts of lung and tumor volumes on lung dosimetry for nonsmall cell lung cancer

摘要

The purpose of this study was to determine the impacts of lung and tumor volumes on normal lung dosimetry in three‐dimensional conformal radiotherapy (3DCRT), step‐and‐shoot intensity‐modulated radiotherapy (ssIMRT), and single full‐arc volumetric‐modulated arc therapy (VMAT) in treatment of nonsmall cell lung cancers (NSCLC). All plans were designed to deliver a total dose of 66 Gy in 33 fractions to PTV for the 32 NSCLC patients with various total (bilateral) lung volumes, planning target volumes (PTVs), and PTV locations. The ratio of the lung volume (total lung volume excluding the PTV volume) to the PTV volume (LTR) was evaluated to represent the impacts in three steps. (a) The least squares method was used to fit mean lung doses (MLDs) to PTVs or LTRs with power‐law function in the population cohort (N = 32). (b) The population cohort was divided into three groups by LTRs based on first step and then by PTVs, respectively. The style="fixed-case">MLDs were compared among the three techniques in each style="fixed-case">LTR group ( style="fixed-case">LG) and each style="fixed-case">PTV group ( style="fixed-case">PG). (c) The power‐law correlation was tested by using the adaptive radiation therapy ( style="fixed-case">ART) planning data of individual patients in the individual cohort (N = 4). Different curves of power‐law function with high R² values were observed between averaged style="fixed-case">LTRs and averaged style="fixed-case">MLDs for 3 style="fixed-case">DCRT, ss style="fixed-case">IMRT, and style="fixed-case">VMAT, respectively. In the individual cohort, high R² values of fitting curves were also observed in individual patients in style="fixed-case">ART, although the trend was highly patient‐specific. There was a more obvious correlation between style="fixed-case">LTR and style="fixed-case">MLD than that between style="fixed-case">PTV and style="fixed-case">MLD.