The impact of BRAF mutation status on clinical outcomes with single-agent PD-1 inhibitor versus combination ipilimumab/nivolumab.

Abstract

10024 Background: Nearly half of all metastatic melanoma patients possess the BRAF V600 mutation. Several therapies are approved for BRAF mutant metastatic melanoma, but it is unclear if there is a differential outcome to various immunotherapy regimens. Our aim was to better assess if BRAF mutation status has any impact on survival to combination ipilimumab/nivolumab (I/N) versus single-agent PD-1 inhibitor (PD-1i). Methods: We performed a single center, retrospective analysis on a cohort of patients diagnosed with metastatic or unresectable melanoma from 2012 to 2019 at the University of Michigan who were treated with standard I/N or PD-1i (nivolumab or pembrolizumab). A univariate analysis of progression free survival (PFS) and overall survival (OS) was stratified by treatment type and BRAF mutation status. A multivariate Cox regression of survival was used to compare the effects of the treatment groups adjusted by BRAF status, age, gender, pre-treatment LDH level, prior treatment status, and brain metastases status. Results: 323 patients were identified. 132 had BRAF V600 mutation and 191 had BRAF wildtype (WT) status. 138 patients received I/N and 185 patients received PD-1i. In our univariate analysis, there was no difference in PFS [HR: 0.72, 95% CI, 0.46 – 1.13] or OS [HR: 0.78, 0.44 – 1.38] with I/N versus PD-1i in the BRAF mutant cohort, but there was improved PFS [HR: 0.55, 0.35 – 0.88) and OS [HR: 0.52, 0.28 – 0.95] with I/N compared to PD-1i in the BRAF WT group. In the multivariate analysis, the BRAF WT group continued to show PFS benefit with I/N compared to PD-1i [HR: 0.57, 95% CI, 0.35 – 0.95], but the OS benefit no longer achieved statistical significance [HR: 0.54, 0.28 – 1.03]. Conclusions: Our study results were discordant with the observation in the landmark CheckMate 067 trial, which noted improved PFS and OS with I/N compared to nivolumab alone in the BRAF mutant group and no difference in the BRAF WT group. In our real-world retrospective analysis, I/N over PD-1i should be considered as initial immunotherapy for metastatic melanoma patients regardless of BRAF mutation status, but even more favorably in BRAF WT.