CEA is normally produced in the developing gastrointestinal tract of the human fetus. Production stops shortly after birth and is normally found in very low concentrations in the blood of adults. Serum levels of CEA may be elevated in heavy smokers.
As a tumor marker, CEA is associated with colon cancer, in which CEA measurement is mainly used to monitor colorectal carcinoma treatment, to identify recurrences after surgical resection, and for staging to determine the degree of metastasis.2
CEA may also be elevated in malignancies of other tissues, including the stomach, pancreas, breast, lung, and thyroid. Because of this relative low specificity for a tissue or organ system, is not recommended for use as a screening tool.