Concurrent immunotherapy is associated with increased radiation necrosis risk in lung cancer patients with brain metastases treated with stereotactic radiosurgery

Purpose The aim of this study was to evaluate the factors associated with local control and radiation necrosis (RN) after stereotactic radiosurgery (SRS) in patients with brain metastases from lung cancer.Patients and methods This study is a retrospective single-center cohort study. The primary endpoint is the occurrence of RN, with the secondary endpoint being local control for each patient. Logistic regression analyses with Firth’s penalization were used to assess risk factors affecting RN. The risk factors affecting the local control were analyzed via Cox regression analyses. Local control and radiation necrosis-free survival (RNFS) were calculated using the Kaplan-Meier method.Results Among the 136 patients in the study, 22 (16.2%) developed RN. The median time to the development of RN was 11.73 months. Concurrent immunotherapy during SRS, prior whole-brain radiation therapy (WBRT), and a planning target volume (PTV) ≥6.37 cm3 are statistically associated with a higher risk of RN. Furthermore, BED10 ≥ 46.325 Gy was significantly associated with improved local control.Conclusions In patients with lung cancer undergoing SRS for brain metastases, factors including prior WBRT, a larger PTV, and concurrent immunotherapy were significantly associated with the development of RN.