Colorectal Cancer with BRAF D594G Mutation Is Not Associated with Microsatellite Instability or Poor Prognosis

Abstract

Objective:BRAF D594G mutations in colorectal cancer patients are not clearly understood. We retrospectively investigated the clinicopathological features of colorectal cancers with BRAF D594G mutations. Methods: We selected 908 colorectal cancer patients who underwent surgical resection from January 2008 to January 2013, and assessed BRAF, KRAS, microsatellite instability, and CpG island methylator phenotype (CIMP). Results: We detected BRAF D594G in 7 patients and BRAF V600E in 45 patients. The clinicopathological features of cancers with BRAF D594G mutation were similar to those with BRAF wild-type, but differed from those with BRAF V600E mutations. Regarding microsatellite instability status, 44.4% of cases with BRAF V600E mutations exhibited high microsatellite instability, compared to 14.3% of those with BRAF D594G mutations and 4.4% of those with BRAF wild-type. There were no CIMP-positive tumors in cancers with BRAF D594G mutations, whereas 67.8% of tumors with BRAF V600E mutations were CIMP-positive. In stage IV cancers, the survival rates of patients at 2 years were 8.5, 50.0, and 68.2% in the BRAF V600E mutation, BRAF D594G mutation, and BRAF wild-type groups, respectively. Conclusion: Colorectal cancers with BRAF D594G mutations exhibit similar clinicopathological features, microsatellite instability status, and prognosis as those with BRAF wild-type.