Objective: The aim of this meta-analysis is to evaluate the distribution pattern of KRAS and BRAF mutations in colorectal cancer.
Materials and methods: The database was searched without language restrictions. Meta-analyses were conducted using the STATA software. We calculated the odds ratio (OR) and its 95% confidence interval (95% CI) to estimate the distribution of and correlation between KRAS and BRAF mutations, CpG island methylator phenotype (CIMP), and microsatellite instability (MSI) in left- and right-sided colorectal cancer.
Results: The studies were divided into five groups: (1) distribution of KRAS/BRAF mutations in distal and proximal colorectal cancer, the summary OR value was 1.24 versus 4.03, (2) distribution of KRAS/BRAF mutations in CIMP-low/Neg and CIMP-high (CIMP-H) tumors, the summary OR value was 0.77 versus 10.49, (3) distribution of KRAS/BRAF mutations in MSI-low (MSI-L)/microsatellite stable (MSS) and MSI-high (MSI-H) tumors, the summary OR value was 0.51 versus 9.60, (4) proportion of CIMP-H/MSI-H tumors among distal and proximal colorectal tumors, the summary OR value was 3.66 versus 6.54, and (5) proportion of CIMP-H tumors among MSI-L/MSS and MSI-H tumors, the summary OR value was 5.87.
Conclusion: The meta-analysis reveals that KRAS has a slightly higher mutation rate in MSI-L/MSS tumors. Moreover, BRAF mutations have higher detection rates in right-sided colorectal cancer, which suggests that BRAF mutations are likely in CIMP-H tumors. Therefore, based on these findings, the molecular diagnostic tests to be conducted in colorectal cancer patients can be determined according to the location/clinical features of the tumor.