BRAF mutation as a pejorative marker in metastatic melanoma.

Abstract

8555 Background: BRAF mutation in melanoma has been shown to be associated with a trend in favour of a spontaneous worse outcome after metastases in a series of 197 patients in Australia. Objective: To correlate BRAF status in metastatic melanoma with clinicopathologic features and outcome. Methods: In our department in France 182 patients with metastatic melanoma have been tested for BRAF mutation between September 2009 and September 2011. Survival was assessed by log-rank test. Multivariate analysis was performed with Cox model. Results: From 182 patients, 88 (48.3%) were B-RAF mutant; 77 (87.5%) V600E, 4 (4.5%) V600K, and 7 (8%) other mutation subtypes. BRAF-mutant patients were younger than BRAF wild-type patients at diagnosis of primary melanoma (median age 52.3 vs 60.7 years, respectively, p=0.003), and at diagnosis of distant metastasis (median age 53.6 vs 64.1 years respectively, p=0.002). 34 patients were treated by B-RAF inhibitors. There was no significant difference in other demographic features of patients with metastatic melanoma by mutation status. Features of the primary melanoma significantly associated with a BRAF mutation (p<0.05) were histopathologic subtype (SSM), high mitotic rate (≥1/mm2), lower Breslow thickness (median Breslow: 2.2 vs 3.5 mm for BRAF mutant and BRAF-wild-type patients respectively, p=0.016), truncal location and location on occasionally exposed at sun site.The interval from diagnosis of first ever melanoma to first distant metastasis was not significantly different in BRAF-mutant and wild-type patients. The median overall survival (OS) from diagnosis of primary melanoma was 6.5 years for BRAF wild-type patients. Median OS was not reached in BRAF-mutant patients treated (34 of 88) with a BRAF inhibitor, but also in those not treated (p=0.24, and p=0.06 for treated BRAF-mutant vs BRAF wild-type). The overall survival from diagnosis of first distant metastasis was not significantly different (p=0.75). These results remained unchanged in a multivariate analysis. Conclusions: Our results confirm the characteristics of BRAF-mutant metastatic patients, and the efficacy of B-RAF inhibitors, but not that the presence of mutant-BRAF is per se a pejorative predictive marker.