UC San Diego

Background

Oncogenic BRAF mutations have been found in diverse malignancies and activate RAF/MEK/ERK signaling, a critical pathway of tumorigenesis. We examined the clinical characteristics and outcomes of patients with mutant (mut) BRAF advanced cancer referred to phase 1 clinic.

Methods

We reviewed the records of 80 consecutive patients with mutBRAF advanced malignancies and 149 with wild-type (wt) BRAF (matched by tumor type) referred to the Clinical Center for Targeted Therapy and analyzed their outcome.

Results

Of 80 patients with mutBRAF advanced cancer, 56 had melanoma, 10 colorectal, 11 papillary thyroid, 2 ovarian and 1 esophageal cancer. Mutations in codon 600 were found in 77 patients (62, V600E; 13, V600K; 1, V600R; 1, unreported). Multivariate analysis showed less soft tissue (Odds ratio (OR) = 0.39, 95%CI: 0.20-0.77, P = 0.007), lung (OR = 0.38, 95%CI: 0.19-0.73, p = 0.004) and retroperitoneal metastases (OR = 0.34, 95%CI: 0.13-0.86, p = 0.024) and more brain metastases (OR = 2.05, 95%CI: 1.02-4.11, P = 0.043) in patients with mutBRAF versus wtBRAF. Comparing to the corresponding wtBRAF, mutBRAF melanoma patients had insignificant trend to longer median survival from diagnosis (131 vs. 78 months, p = 0.14), while mutBRAF colorectal cancer patients had an insignificant trend to shorter median survival from diagnosis (48 vs. 53 months, p = 0.22). In melanoma, V600K mutations in comparison to other BRAF mutations were associated with more frequent brain (75% vs. 36.3%, p = 0.02) and lung metastases (91.6% vs. 47.7%, p = 0.007), and shorter time from diagnosis to metastasis and to death (19 vs. 53 months, p = 0.046 and 78 vs. 322 months, p = 0.024 respectively). Treatment with RAF/MEK targeting agents (Hazard ratio (HR) = 0.16, 95%CI: 0.03-0.89, p = 0.037) and any decrease in tumor size after referral (HR = 0.07, 95%CI: 0.015-0.35, p = 0.001) correlated with longer survival in mutBRAF patients.

Conclusions

BRAF appears to be a druggable mutation that also defines subgroups of patients with phenotypic overlap, albeit with differences that correlate with histology or site of mutation.