The overall response rate of patients with wild-type K-ras to cetuximab is only 40–60%, but the response rate of patients with K-ras mutations was only 10% or less [10,11], thus, in this study, we detected K-ras mutations to predict the efficacy of EGFR-TK inhibitor cetuximab in Chinese patients with metastatic colorectal cancer. This evidence concerns the gene KRAS and metastatic colorectal cancer.