Adverse Radiation Effect and Disease Control in Patients Undergoing Stereotactic Radiosurgery and Immune Checkpoint Inhibitor Therapy for Brain Metastases

Background Immune checkpoint inhibitors (ICIs) and stereotactic radiosurgery (SRS) are increasingly used together to manage brain metastases (BMs). We assessed adverse radiation effect, disease control, and overall survival in patients with BMs who received SRS with anticytotoxic T-lymphocyte–associated protein 4 and/or anti– programmed cell death protein receptor/ligand therapies. Methods We retrospectively reviewed the records of patients with intact or resected BMs treated with SRS and ICIs within 5 months of SRS between 2010 and 2018. Patients were defined as receiving concurrent SRS and ICI if a dose of ICI was given within 4 weeks of SRS. Local failure, distant intracranial failure, extracranial failure, and adverse radiation effect were assessed using cumulative incidence rates and competing risk regressions with death as a competing risk. Overall survival was assessed using the Kaplan-Meier method and Cox proportional hazards models. Results A total of 97 patients with 580 BMs were included in our analysis. Competing risk analyses showed that concurrent SRS-ICI therapy is associated with higher rates of adverse radiation effect (6.4% vs. 2.0% at 1 year; multivariable hazard ratio [HR], 4.47; 95% confidence interval [CI], 1.57–12.73; P = 0.005), lower rates of extracranial failure (69.7% vs. 80.8% at 1 year; multivariable HR, 0.60; 95% CI, 0.42–0.87; P = 0.007), and better overall survival (48.6% vs. 25.4% at 1 year; multivariable HR, 0.57; 95% CI, 0.33–0.99; P = 0.044) compared with nonconcurrent therapy. SRS-ICI timing was not associated with local failure or distant intracranial failure. Conclusions Concurrent SRS-ICI therapy has a tolerable adverse event profile and may improve extracranial disease control and overall survival, supporting concurrent use in the management of BMs.