Melanoma brain metastases harboring BRAF V600K or NRAS mutations are associated with an increased local failure rate following conventional therapy

Abstract

Studies on melanoma brain metastases (MBM) with regard to mutational status are lacking. We investigated the outcomes of MBM in molecularly characterized patients for BRAF and NRAS mutations receiving conventional treatment. We investigated associations between outcomes [competing risk of local and distant brain failure (LF, DF) and overall survival (OS)] and clinical/pathological features of patients with known mutation status following initial treatment of MBM. Competing risk analysis was performed using the methods of Fine and Gray. We identified 235 patients with MBM diagnosed from 2005 to 2011. Mutation prevalence was BRAF ^non-V600K 98 (42%), BRAF ^V600K 34 (14%), NRAS 43 (18%), and wild-type for both genes (WT) 60 (26%) patients. Six month cumulative incidence LF rates were 3% for combined SRS or surgery with adjuvant radiation, 18% for surgery, 18% for SRS, 60% for WBRT, and 67% for systemic therapy. On multivariate analysis, only mutation status and initial treatment type were found to be independent predictors of local control. As compared to WT, NRAS (HR 2.58, 95% CI 1.18–5.67, p = 0.02) and BRAF ^V600K (HR 2.83, 95% CI 1.23–6.47, p = 0.01) mutational status were statistically significant while BRAF ^non-V600K status was not statistically significant (p = 0.23). Mutation status was not associated with DF or OS. BRAF ^V600K and NRAS mutation status predict increased LF following conventional treatments for MBM. These data can inform the design and interpretation of future MBM trials.

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