CEA is used mainly to monitor the treatment of cancer patients, especially those with colon cancer. Following surgery, CEA values are helpful in monitoring the response to therapy and in determining whether the disease has recurred. CEA is also used as a marker for other forms of cancer, including cancers of the rectum, lung, breast, liver, pancreas, stomach, and ovary. Not all cancers produce CEA, and a positive CEA test is not always due to cancer. Therefore, CEA is not used for screening the general population.

A CEA test may be ordered when your symptoms suggest the possibility of cancer. In patients who have been diagnosed with certain types of cancer, a CEA level is also measured before and after therapy, to evaluate the success of treatment.

On initial testing, patients with smaller and early-stage tumors are likely to have normal or only slightly elevated CEA values. Patients with more advanced tumors or tumors that have spread throughout the body are more likely to have high CEA values. When CEA levels decrease after therapy, it means that most or all of the CEA-producing tumor has been removed. A steadily rising CEA level is often the first sign of tumor recurrence.

Increased CEA levels can indicate some non-cancer-related conditions, such as inflammation, cirrhosis, peptic ulcer, ulcerative colitis, rectal polyps, emphysema, and benign breast disease.

Since not all cancers produce CEA, it is possible to have cancer but also have a normal CEA level.

Individuals who smoke cigarettes tend to have higher CEA levels than non-smokers.

When cancer spreads to other organs, CEA may be present in other bodily fluids besides blood. For example, if CEA is detected in cerebrospinal fluid, this may indicate a central nervous system metastasis.