Carcinoembryonic Antigen (CEA)

CEA stands for carcinoembryonic antigen. CEA is a substance found on the surface of some cells. It is a type of glycoprotein produced by cells of the gastrointestinal tract during embryonic development. It is produced in very small amounts after birth. The level of CEA in the bloodstream is thus relatively low unless certain diseases - including certain forms ofcancer- are present.

CEA is most frequently tested in blood. It can also be tested in body fluids and in biopsy tissue.

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

The best use of CEA is as a tumor marker, especially forcancersof the gastrointestinal tract. When the CEA level is abnormally high before surgery or other treatment, it is expected to fall to normal following successful surgery to remove all of thecancer. A rising CEA level indicates progression or recurrence of thecancer. This must be confirmed , as the CEA test by itself is not specific enough to substantiate a recurrence of a cancer. In addition, levels >20 ng/ml before therapy may be associated with cancer which has already spread (metastatic disease).

Both benign (harmless) andmalignant(cancerous) conditions can increase the CEA level. The most frequent cancer which causes an increased CEA iscancer of the colonand rectum. Others include cancers of the pancreas, stomach, breast, lung, and medullarycarcinoma of the thyroidandovarian cancer. Benign conditions which can elevate CEA includesmoking, infections,inflammatory bowel disease,pancreatitis,cirrhosisof theliver, and some benign tumors in the same organs in which an elevated CEA indicates cancer. Chemotherapy andradiation therapycan cause a temporary rise in CEA due to the death of tumor cells and release of CEA into the blood stream. Changing levels of CEA during cancer treatment must always be correlated with other clinical findings. While worrisome, changes in CEA are not diagnostic of cancer progression on their own.

CEA is not an effective screening test for hidden (occult) cancer since early tumors may 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.