Carcinoembryonic Antigen (CEA)

Carcinoembryonic antigen (CEA) is a glycoprotein involved in cell adhesion. It is normally produced during fetal development, but the production of CEA stops before birth. Therefore, it is not usually present in the blood of healthy adults, although levels are raised in heavy smokers. CEA is a glycosyl phosphatidyl inositol (GPI)-cell surface anchored glycoprotein whose specialized sialofucosylated glycoforms serve as functional colon carcinoma L-selectin and E-selectin ligands, which may be critical to the metastatic dissemination of colon carcinoma cells

The normal range for CEA in an adult non-smoker is <2.5 ng/ml and for a smoker <5.0 ng/ml.

What conditions can cause an elevated CEA?

Both benign and malignant (harmless and cancerous) conditions can increase the CEA level. The most frequent cancer which causes an increased CEA is cancer of the colon and rectum. Others include cancers of the pancreas, stomach, breast, lung, and certain types of thyroid and ovarian cancer. Benign conditions which can elevate CEA include smoking, infections, inflammatory bowel disease, pancreatitis, cirrhosis of the liver, and some benign tumors in the same organs in which an elevated CEA indicates cancer. Chemotherapy and radiation therapy can cause a temporary rise in CEA due to the death of tumor cells and release of CEA into the blood stream. Benign disease does not usually cause an increase above 10 ng/ml.

What are the limitations of CEA testing?

CEA is not an effective screening test for hidden (occult) cancer since early tumors do not cause significant blood elevations. Also, many tumors never cause an abnormal blood level, even in advanced disease. Because there is variability between results obtained between laboratories, the same laboratory should do repeat testing when monitoring a patient with cancer.