Effects of different techniques in stereotactic radiotherapy for non-small cell lung cancer based on RTOG 0813/0915 dosimetry index

Objective To systematically evaluate the differences of non-small cell lung cancer-stereotactic body radiation therapy (NSCLC-SBRT) techniques such as conformal radiotherapy (CRT), dynamic conformal arc therapy (DCAT), intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in The Radiation Therapy Oncology Group (RTOG) 0813/0915 dosimetric index, other whole-lung dose index, and treatment efficacy, and to select appropriate NSCLC-SBRT technology. Methods A total of 17 NSCLC patients who underwent SBRT from April 2019 to March 2021 were enrolled and their clinical data were retrospectively analyzed. The plans included 7-beam CRT, 7-beam IMRT, double arc DCAT and double arc VMAT. They were compared for conformity index (R_100%), ratio of 50% isodose volume to the PTV (R_50%), maximum dose 2 cm away from PTV in any direction (D_2cm), and percent of normal lung receiving 20 Gy (V₂₀) and therapeutic efficacy. Results In terms of target volume R_100%, R_50% and D_2cm in the four plans, the VMAT group was the best (P＜0.05), followed by the IMRT group (P＜0.05), the CRT and DCAT groups were worse and the difference between the two groups was without statistical difference. The VMAT and IMRT groups had similar percent of normal lung receiving 5 Gy (V₅), V₂₀ and mean dose (D_mean) (P=0.082, P=0.082, and P=0.652), where the total lung V₂₀ of the VMAT group was 13.3% and 9.3% lower than that of the CRT and DCAT groups, respectively (P＜0.05). Compared with the IMRT group, the total lung percent of normal lung receiving 10 Gy (V₁₀), monitor units (MUs) and treatment time of the VMAT group decreased by 6.9%, 53.1% and 18.1%, respectively (P＜0.05), and the V₁₀, MUs and treatment time of the DCAT group decreased by 65.4% and 36.4%, respectively (P＜0.05). Compared with the VMAT group, the number of MUs and treatment time in the DCAT group decreased by 26.1% and 22.3%, respectively (P＜0.05). Conclusions For NSCLC-SBRT based on medical accelerators, VMAT is preferred, which can not only ensure the dose limit requirements of the RTOG protocol but also reduce the total lung dose.