What is a CEA test?

CEA stands for carcinoembryonic antigen. It is a protein found in the tissues of a developing baby. CEA levels normally become very low or disappear after birth. Healthy adults should have very little or no CEA in their body.

This test measures the amount of CEA in the blood, and sometimes in other body fluids. CEA is a type of tumor marker. Tumor markers are substances made by cancer cells or by normal cells in response to cancer in the body.

A high level of CEA can be a sign of certain types of cancers. These include cancers of the colon and rectum, prostate, ovary, lung, thyroid, or liver. High CEA levels may also be a sign of some noncancerous conditions, such as cirrhosis, noncancerous breast disease, and emphysema.

A CEA test can’t tell you what kind of cancer you have, or even whether you have cancer. So the test is not used for cancer screening or diagnosis. But if you’ve already been diagnosed with cancer, a CEA test can help monitor the effectiveness of your treatment and/or help find out if the disease has spread to other parts of your body.

Other names: CEA assay, CEA blood test, carcinoembryonic antigen test

What is it used for?

A CEA test may be used to:

  • Monitor treatment of people with certain types of cancers. These include colon cancer and cancers of the rectum, prostate, ovary, lung, thyroid, and liver.
  • Figure out the stage of your cancer. This means checking the size of the tumor and how far the cancer has spread.
  • See if cancer has returned after treatment.

Why do I need a CEA test?

You may need this test if you’ve been diagnosed with cancer. Your health care provider may test you before you start treatment, and then regularly throughout the course of your therapy. This can help your provider see how well your treatment is working. You may also get a CEA test after you’ve completed treatment. The test can help show whether the cancer has come back.

What happens during a CEA test?

CEA is usually measured in the blood. During a CEA blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Sometimes, CEA is tested in the spinal fluid or from fluid in the abdominal wall. For these tests, your provider will remove a small sample of fluid using a thin needle and/or syringe. The following fluids may be tested:

  • Cerebrospinal fluid (CSF), a clear, colorless liquid found in the spinal cord
  • Peritoneal fluid, a fluid that lines your abdominal wall
  • Pleural fluid, a liquid inside your chest cavity that covers the outside of each lung

Will I need to do anything to prepare for the test?

You don’t need any special preparations for a CEA blood test or a pleural fluid test.

You may be asked to empty your bladder and bowels before a CSF or peritoneal fluid test.

Are there any risks to the test?

There is very little risk to having a CEA blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

CEA tests of body fluids are usually very safe. Serious problems are rare. But you may experience one or more of the following side effects:

  • If you had a CSF test, you may feel some pain or tenderness in your back at the site where the needle was inserted. Some people get a headache after the test. This is called a post-lumbar headache.
  • If you had a peritoneal fluid test, you may feel a little dizzy or lightheaded after the procedure. There is a small risk of damage to the bowel or bladder, which may cause an infection.
  • If you had a pleural fluid test, there is a small risk of lung damage, infection, or blood loss.

What do the results mean?

If you were tested before you started treatment for cancer, your results may show:

  • A low level of CEA. This may mean your tumor is small and the cancer has not spread to other parts of your body.
  • A high level of CEA. This may mean you have a larger tumor and/or your cancer may have spread.

If you are being treated for cancer, you may be tested several times throughout treatment. These results may show:

  • Your levels of CEA started high and remained high. This may mean your cancer is not responding to treatment.
  • Your levels of CEA started high but then decreased. This may mean your treatment is working.
  • Your CEA levels decreased, but then later increased. This may mean your cancer has come back after you’ve been treated.

If you had a test on a body fluid (CSF, peritoneal, or pleural), a high level of CEA may mean the cancer has spread to that area.