• Linda Chen, Jacqueline Douglass, Lawrence Kleinberg, Xiaobu Ye, Ariel E Marciscano, Patrick M Forde, Julie Brahmer, Evan Lipson, William Sharfman, Hans Hammers, Jarushka Naidoo, Chetan Bettegowda, Michael Lim, and Kristin J Redmond.
• Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins Hospital, Baltimore, Maryland.
• Int. J. Radiat. Oncol. Biol. Phys. 2018 Mar 15; 100 (4): 916-925.

PurposeTo characterize the effect of concurrent stereotactic radiosurgery-stereotactic radiation therapy (SRS-SRT) and immune checkpoint inhibitors on patient outcomes and safety in patients with brain metastases (BMs).Methods And MaterialsWe retrospectively identified metastatic non-small cell lung cancer, melanoma, and renal cell carcinoma patients who had BMs treated with SRS-SRT from 2010 to 2016 without prior whole-brain radiation therapy. We included SRS-SRT patients who were treated with anti-cytotoxic T-lymphocyte-associated protein 4 (ipilimumab) and anti-programmed cell death protein 1 receptor (nivolumab, pembrolizumab). Patients who were given immune checkpoint inhibitors on active or unreported clinical trials were excluded, and concurrent immune checkpoint inhibition (ICI) was defined as ICI given within 2 weeks of SRS-SRT. Patients were managed with SRS-SRT, SRS-SRT with nonconcurrent ICI, or SRS-SRT with concurrent ICI. Progression-free survival and overall survival (OS) were estimated using Kaplan-Meier survival curves, and Cox proportional hazards models were used for multivariate analysis. Logistic regression was used to identify predictors of acute neurologic toxicity, immune-related adverse events, and new BMs.ResultsA total of 260 patients were treated with SRS-SRT to 623 BMs. Of these patients, 181 were treated with SRS-SRT alone, whereas 79 received SRS-SRT and ICI, 35% of whom were treated with concurrent SRS-SRT and ICI. Concurrent ICI was not associated with increased rates of immune-related adverse events or acute neurologic toxicity and predicted for a decreased likelihood of the development of ≥3 new BMs after SRS-SRT (P=.045; odds ratio, 0.337). Median OS for patients treated with SRS-SRT, SRS-SRT with nonconcurrent ICI, and SRS-SRT with concurrent ICI was 12.9 months, 14.5 months, and 24.7 months, respectively. SRS-SRT with concurrent ICI was associated with improved OS compared with SRS-SRT alone (P=.002; hazard ratio [HR], 2.69) and compared with nonconcurrent SRS-SRT and ICI (P=.006; HR, 2.40) on multivariate analysis. The OS benefit of concurrent SRS-SRT and ICI was significant in comparison with patients treated with SRS-SRT before ICI (P=.002; HR, 3.82) or after ICI (P=.021; HR, 2.64).ConclusionsDelivering SRS-SRT with concurrent ICI may be associated with a decreased incidence of new BMs and favorable survival outcomes without increased rates of adverse events.Copyright © 2017 Elsevier Inc. All rights reserved.

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