Carcinoembryonic

Carcinoembryonic antigen (CEA) is a glycoprotein involved in cell adhesion, encoded by the CEACAM5 gene and belonging to the immunoglobulin superfamily. It is normally expressed at very low levels in most adult tissues but is abundant during fetal development, particularly in the gastrointestinal tract. In malignant cells, CEA is often overexpressed and released into the bloodstream, leading to measurable levels in blood tests.

CEA is primarily used as a tumor marker in oncology. Blood levels are measured by immunoassay and reported in nanograms per milliliter. Normal reference ranges vary by assay and laboratory, but commonly are 0-3 ng/mL for non-smokers and up to about 5 ng/mL for smokers; many labs use 5 ng/mL as the upper limit of normal. Elevated levels can indicate tumor burden and are used to monitor treatment response and detect recurrence in colorectal cancer and, to a lesser extent, pancreatic, gastric, breast, and medullary thyroid carcinomas.

CEA is not cancer-specific and can be elevated in benign conditions such as hepatitis, cirrhosis, pancreatitis, and inflammatory bowel disease, and in smokers. Some cancers may not produce CEA, so a normal level does not exclude malignancy. After curative treatment, CEA levels typically fall with a half-life of about 3-7 days; rising or persistently elevated levels may suggest residual disease or recurrence.

See also: CEACAM5, carcinoembryonic antigen-related cell adhesion molecules.