Benign conditions that can increase CEA include smoking, infection, inflammatory bowel disease, pancreatitis, cirrhosis of the liver, and some benign tumors (in the same organs which have cancers with increased CEA). Benign disease does not usually cause a CEA increase over 10 ng/ml.
The main use of CEA is as a tumor marker, especially with intestinal cancer. The most common cancers that elevate CEA are in the colon and rectum. Others: cancer of the pancreas, stomach, breast, lung, and certain types of thyroid and ovarian cancer. Levels over 20 ng/ml before therapy are associated with cancer which has already metastasized (spread).
CEA is useful in monitoring the treatment of CEA-rich tumors. If the CEA is high before treatment, it should fall to normal after successful therapy. A rising CEA level indicates progression or recurrence of the cancer. (Chemotherapy and radiation therapy can themselves cause a rise in CEA due to death of tumor cells and release of CEA into the blood stream but that rise is typically temporary).
"Carcinoembryonic" reflects the fact that CEA is made by some cancers ("carcino-") and by the developing fetus ("-embryonic").