Abstract
BACKGROUND: BRAF(V600E) mutations occur in fewer than 10% of all patients with metastatic colorectal cancer (CRC) and arise from sessile serrated adenomas. Despite efficacy with targeted therapies against MAPK signaling and with immunotherapies in this population, survival outcomes for patients with BRAF(V600E) mutated metastatic CRC in general are poor. Characteristics distinguishing patients with BRAF(V600E) mutated metastatic CRC with favorable versus unfavorable outcomes have not been well annotated. METHODS: Records of 187 patients with BRAF(V600E) mutated metastatic CRC evaluated at MD Anderson Cancer Center between 2005-2020 were reviewed. Patients with the shortest and longest metastatic survival (N=25 for each group) were compared. Associations between prognostic group and clinical/pathologic features were measured by odds ratio and for median survival by log-rank testing. RESULTS: Median metastatic survival differed between the 2 BRAF(V600E) mutated metastatic CRC populations (8.6 vs. 83.9 months, hazard ratio 32; P<0.0001). Patients with poor survival more commonly had hepatic involvement [75% vs. 28%, odds ratio (OR) 8.1, 95% confidence interval (CI): 2.3-29; P=0.001]. Patients with favorable survival were more likely to develop metachronous metastases (52% vs. 16%, OR 5.7, 95% CI: 1.5-21; P=0.01) and undergo definitive locoregional therapy to metastatic disease (40% vs. 0%, OR 34.5, 95% CI: 1.9-630; P=0.01). Microsatellite instability (36% vs. 4%, OR 19.8, 95% CI: 2.2-180; P=0.008) and prior tobacco exposure (44% vs. 16%, OR 4.1, 95% CI: 1.1-15.6, P=0.04) were associated with a favorable prognosis. Durable responses to MAPK-targeted therapies and immunotherapy were noted in the favorable group. CONCLUSIONS: A small fraction of patients with BRAF(V600E) mutated metastatic CRC can achieve excellent long-term survival which belies conventional context and is driven by either surgical metastectomy or by systemic treatment options. While poor overall prognosis remains the recognized outcome for most patients with BRAF(V600E) mutated metastatic CRC, it is possible that few may achieve exceptionally favorable survival.