CEACAM5 and colorectal carcinoma: According to our retrospective analysis in large series of case investigation, the high rate of preoperative CEA was only 38.04% in 1969 CRC patients (JiaLiang et al., 2013), which suggested that most of the patients belonged to the preoperative CEA-normal CRC patients and would be lack of efficient serum biomarkers for CRC patients to monitor and follow-up after treatment.