Abstract

Objective: Mutation in KRAS gene is one of the most common genetic changes among patients with colorectal cancer (CRC), which is observed in 30-45 of cases. This study aims to estimate the prevalence of this mutation among patients with primary or metastatic CRC. Patients and Methods: Eligible studies were identified during a comprehensive electronic search, applying inclusion/exclusion criteria and quality assessment. Stata version 11 software was used for data analysis. The heterogeneity between the results of the primary studies was assessed using Cochrane and I-square indices. Random effect model was applied for combining the primary estimates. Point and pooled estimates (with 95 confidence intervals) were presented by forest plots. Investigating the factors associated with heterogeneity was carried out using meta-regression models. The publication bias was traced by Egger test. Results: Combining the results of 164 eligible studies, the total prevalence of KRAS gene mutation among primary tumor samples was estimated as of 33.14 (95 confidence interval: 30.08-36.20). The corresponding figure for metastatic cancer was estimated as of 36.20 (95 confidence interval: 33.96-38.44). Prevalence of this mutation among patients with primary CRC in EMRO, EURO, PAHO, SEARO and WAPRO was 30.23, 35.12, 31.83, 33.17 and 32.64, respectively. Corresponding rates for mutation among metastatic cases were 42.20, 38.46, 36.06, 42.80, 33.05, respectively. In addition, the total prevalence of KRAS gene mutation in codons 12 and 13 was estimated as 76.69 and 28.49, respectively. Conclusions: More than one-third of patients with CRC carried KRAS gene mutation particularly in the metastatic tumors. The rate of mutation was the same in different WHO regions.