The pooled frequency of MLH1 promoter methylation was 14.0% (95% CI: 10.2–19.0%) in 353 KRAS-mutated and 21.8% (95% CI: 13.2–33.8%) in 570 wild-type CRC, in three studies [15], [21], [22] (pooled OR = 0.476; 95% CI: 0.322–0.703; P<0.001; I2 = 49.293%) (Table 2 and Table 3). This evidence concerns the gene MLH1 and colorectal carcinoma.