To detect mutations of K-ras gene in cancer tissues and preoperative carcinoembryonic antigen in serums of patients with colorectal cancer, and to find out their correlation with clinical pathological characteristics of colorectal cancer.

The specimens of 100 patients with colorectal cancer were collected. Real-time fluorescence quantitative PCR and DNA sequencing were performed in these tissues to detect K-ras gene mutations at codon 12th and codon 13th, and preoperative carcinoembryonic antigen level in serums were evaluated by radioimmunoassay, the results were analyzed with patients' clinical pathological data.

Thirty-nine cases (39.0%) were detected pointmutation, and 31(31.0%)cases were found pointmutation at codon 12th, eight cases(8.0%) at codon 13th. The rate of K-ras gene mutation in cases with metastatic lymph nodes(57.8%) was higher than that in cases with no metastatic lymph node(23.6%). The mutation rate in cases with liver metastasis(62.5%) was higher than that in cases without liver metastasis(34.5%), P<0.05. And significant differences were found between TNM III, IV(56.5%) and TNM I, II(24.1%). There were no closely relationship with size, location, invasive depth and differentiation extent of tumor. CEA levels in 49 patients were positive (more than 5μg/L). Patients with lymph node or liver metastasis had a high lever of CEA. The positive rate of CEA level in patients with liver/lymph node metastasis was 75% and 73.3% respectively, which was higher than that in patients without liver/lymph node metastasis(44%, 29.1%), P<0.05. Significant differences between Duke′s stages/TNM stages were found with high positive rate in the groups of Duke′s D stage and TNM III, IV stages. CEA levels had no relationship with size, location, invasive depth or differentiation extent of tumor.

K-ras gene mutation and CEA level are closely associated with liver and/or lymph node metastasis in colorectal cancer. They are negative prognostic factors of colorectal cancer.