Carcinoembryonic antigen (CEA), a structurally complex acidic glycoprotein, is a broad-spectrum tumor marker found mainly in adult cancer tissue as well as in fetal gastrointestinal tissue.
1.Screening
Serum CEA is generally not used for tumor screening in asymptomatic people.
2.Ancillary Diagnosis
①　Serum CEA is a relatively broad-spectrum tumor marker. It can be used clinically for the auxiliary diagnosis of colon cancer, rectal cancer, lung cancer, breast cancer, esophageal cancer, pancreatic cancer, gastric cancer, metastatic liver cancer and other common tumors. Other malignant tumors such as medullary thyroid cancer, bile duct cancer and urological malignant tumors also have different degrees of positive rate.
②　Serum CEA can also be elevated to varying degrees in pregnancy, colitis, colon polyps, intestinal diverticulitis, pancreatitis, cirrhosis, hepatitis, benign lung disease, and cardiovascular disease, but the percentage of positivity is low.
3.Prognostic assessment
CEA level in serum is one of the factors to determine the prognosis of tumor. Persistent elevation of serum CEA indicates bad prognosis.
4.Treatment and recurrence monitoring
①　For those with elevated CEA before treatment, if surgery, chemotherapy, targeted therapy or immunotherapy are effective, the serum CEA concentration will drop to within the reference interval; if the serum CEA only partially decreases or does not decrease after treatment, it means the treatment is not effective.
②　Serum CEA can be used for follow-up and recurrence monitoring after tumor treatment. Generally, it is advisable to test every 3 months for 2 years after treatment and every 6 months for 3 to 5 years.