Outcomes of melanoma patients with brain metastases receiving immune checkpoint inhibitor (ICI) therapy.

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e21028 Background: The effect of ICI therapy on brain metastasis (mets) in melanoma patients has been described, however the impact of genomic alterations and local treatment (trt) including radiation therapy (RT) on CNS outcomes and overall survival (OS) has not yet been explored. Methods: Under institutional IRB approval, we reviewed our electronic medical record to identify patients (pts) with metastatic melanoma and brain mets who received trt with ICI. Trt history, CNS responses as indicated by the treating physician and available genomic data were recorded. OS was estimated using a multivariable Cox regression model adjusting for genomic alteration, age, ICI regimen and brain mets. Results: A total of 49 pts were identified (65% male). Thirty seven pts had testing for tumor genomic alterations (alt, hotspot and comprehensive genomic testing); BRAFV600E( 30%), cKIT(5%), NRAS(16%), no alt (38%). Prior to initiation of ICI, 78% had known CNS mets, of these, 61% received RT. There was no difference in median OS for pts who started RT prior to ICI compared to those without RT (mOS = 75.71 vs 49.4 weeks, p = 0.75). Median OS was improved for those pts who received RT > 90 days prior to initiation of ICI trt however this was not statistically significant (45.7 vs 136 weeks, p = 0.12) and HR = 0.45 (95% CI 0.08, 2.36). OS was not significantly different in pts with genomic alterations compared with those without alterations (p = 0.264). Of the pts with known brain mets at the time of ICI start, 34% had progressive disease at 3 months and 11% were felt to have pseudoprogression. 18% survived to undergo 6-month disease assessment, of these 12% had further progression. All pts with cKIT mutations survived to 6-month disease assessment. 75% of pts with known brain mets developed new lesions, 15% had increased mass size. Pts who developed new brain mets while on trt with ICI had worse survival than those with preexisting brain mets and developed new brain lesions (28 vs 58 weeks, p = 0.05). 6% of all pts developed CNS immune related adverse effects. Conclusions: Most patients with melanoma and known brain metastasis prior to ICI developed new brain lesions as a site of metastatic spread. The development of new brain mets was associated with worse outcomes. Neither genomic alterations nor RT prior to ICI start were associated with improved survival.