Local control of stereotactic body radiotherapy with dynamic tumor tracking for lung tumors: a propensity score-matched analysis.

Abstract

Dynamic tumor tracking (DTT) is a method of respiratory motion management in radiotherapy. It reduces the radiation field but risks delivering an insufficient radiation dose to the tumor. We investigated the local control of DTT-stereotactic body radiotherapy (SBRT) for lung tumors. Patients treated with SBRT for early-stage, non-small-cell lung cancer and lung metastases (2013-18) were retrospectively reviewed. Patients with tumor motion >1cm were treated with DTT-SBRT (DTT group); those with tumor motion ≤1cm were treated with static-SBRT (static group). A static planning target volume for the static-SBRT plan was also created for patients in the DTT group, and planning target volume reduction relative to the planning target volume for the DTT-SBRT plan was assessed. Patients were matched in a 1:1 ratio using a propensity score predictive of the SBRT technique. Of the 245 lesions in 218 patients (median follow-up, 25.4months), 69 were treated with DTT-SBRT and 176 with static-SBRT. The median planning target volume reduction in the DTT group was 30.3%. After propensity score matching, 124 lesions were included (62 per group). Two-year local control rates for the DTT and static groups were 94.2 and 95.9%, respectively, for all lesions (P=0.19) and 96.3 and 94.5%, respectively, for matched lesions (P=0.79). In univariate analysis, DTT-SBRT was not associated with local control for all lesions (hazard ratio, 2.06; P=0.20) or matched lesions (hazard ratio, 1.22; P=0.79). No grade 4/5 toxicities were observed. DTT-SBRT for lung tumors reduced the planning target volume, but not local control rates. DTT was useful for respiratory motion management.