CEA test

A CEA test measures the level of carcinoembryonic antigen (CEA) in your blood or other body fluid. As a type of tumor marker, CEA is an indicator of whether cancer is growing and spreading or diminishing with treatment. It is also known as a CEA assay, CEA blood test and carcinoembryonic antigen test. You may be tested before treatment to set a baseline level, then again during and after treatment.

What is CEA?

While in the uterus, an unborn baby produces CEA, but healthy adults produce little or none of this protein. Smokers may have elevated levels of carcinoembryonic antigen, as well as people with the following noncancerous conditions:

• Emphysema
• Cirrhosis 
• Benign breast disease
• Inflammation of the gallbladder (cholecystitis)
• Inflammation of the pancreas (pancreatitis)
• Peptic ulcer
• Ulcerative colitis
• Rectal polyps

High levels correspond to the presence of colorectal cancer, as well as cancers of the pancreas, liver, stomach, ovaries, thyroid, lungs and breast.

Carcinoma refers to cancers that arise from epithelial tissue, which lines and covers organs and includes your skin. Carcinomas make up the bulk of cancer cases—80 to 90 percent, according to the National Cancer Institute. Adenocarcinomas are carcinomas that begin in a gland or organ, often in a mucus membrane. Any cancer classified as an adenocarcinoma may generate CEA.

What is a CEA test used for?

Because many types of cancer and several noncancerous conditions may cause high CEA levels, doctors don’t use CEA tests to diagnose a specific form of cancer or determine whether you have cancer. Rather, they’re used to monitor progress of certain treatments.

CEA is one of several tumor markers. Tumor markers are proteins or other substances that occur in or are produced by cancer cells and are released into the bloodstream. They provide valuable information on a patient’s cancer and how likely it is to respond to certain treatments.

Others tests for cancer include:

• CA-125, an indicator of cancer of the ovaries, fallopian tubes or peritoneum (a layer of tissue enclosing your abdominal organs)
• PSA, or prostate-specific antigen
• HCG, or human chorionic gonadotropin, a sign of cancer of the ovaries, testicles or the spaces between the lungs or behind the intestines
• CA 19-9, associated with cancer of the bile ducts or pancreas

Getting a CEA blood test

Most commonly, CEA tests involve taking a blood sample, a simple procedure where blood is withdrawn from one of your veins via a needle into a syringe or test tube. 

No fasting is required with a CEA blood test, which means there’s no preparation needed on your part.

Getting a CEA fluid test

Less often, your doctor may test for CEA in fluid from other parts of your body, depending upon the type of cancer and where a tumor may be located.

The test may remove:

• Cerebrospinal fluid (from the spine)
• Peritoneal fluid (from the abdomen)
• Pleural fluid (from the area next to the lungs)

You may experience slight discomfort from the needle and soreness and bruising afterward. Before both the spinal and abdominal procedures, you may be asked to go to the bathroom. Although generally considered safe, both the abdominal and pleural fluid tests carry a small risk of tissue damage and infection—as well as possible blood loss for the pleural test.

Test results

Before undergoing cancer treatment, you may have your CEA levels tested.

As a general rule, if you’ve been diagnosed with cancer:

• A low CEA level indicates a small tumor that hasn’t spread elsewhere in the body.
• A high CEA level may correspond to a larger tumor and/or cancer that has spread—or metastasized—to one or more locations away from the original site.

Interpreting your CEA results

Results may be compared with levels taken during and after therapy as a way to better understand how the cancer has responded to treatment.

• If your levels of CEA drop during treatment, this may mean it’s working. The normal range for CEA is 0 to 2.5 nanograms per milliliter of blood (ng/mL).
• If CEA levels remain elevated during treatment, your treatment may not have been as successful as hoped. Anything greater than 10 ng/mL suggests extensive disease, and levels greater than 20 ng/mL suggest the cancer may be spreading.
• If your CEA levels dropped during treatment but are on the rise again, you may be experiencing a recurrence of cancer.

Note that if you smoke, your CEA levels may be high even if you don’t have cancer.