What is a CEA test?

CEA stands for carcinoembryonic antigen. CEA is a protein that is a type of "tumor marker." Tumor markers are substances that are often made by cancer cells or by normal cells in response to cancer.

High levels of CEA are normal in healthy, unborn babies. After birth, CEA levels become very low or disappear completely. So, healthy adults should have little or no CEA in their bodies.

Cancers that may cause high levels of CEA include cancers of the:

• Colon and rectum (colorectal or bowel cancer)
• Prostate
• Ovary
• Lung
• Thyroid
• Liver
• Pancreas
• Breast

If you've been diagnosed with a cancer that can cause high CEA levels, CEA testing may help your health care provider learn more about your cancer and chance of recovery. The test is often used with other tests to check if cancer treatment is working.

CEA tests are not used to screen for or diagnose cancer. That's because:

• Cancers that often cause high CEA levels don't always cause high levels. You can have normal CEA test results even though you have one of these cancers.
• Many other health problems that aren't cancer can make CEA levels rise, including certain conditions that affect your liver, digestion, or breathing.

Most CEA tests use a sample of your blood to measure your CEA level. Sometimes the test uses a sample of fluid from your spine, chest, or abdomen (belly), but this is less common.

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

What is it used for?

A CEA test is mostly used in people who have been diagnosed with cancers that often increase CEA levels. It's most commonly used in colorectal cancer. A provider may order a CEA test along with other tests to:

• Learn more about a cancer soon after it has been diagnosed. CEA levels can help predict the likelihood of recovery and/or the chance that cancer will come back after treatment.
• Check how well cancer treatment is working.
• See if cancer has returned after treatment.

Why do I need a CEA test?

If you've been diagnosed with a type of cancer that can cause high CEA levels, you may need CEA testing:

• Before treatment to:
  • Help understand how serious your cancer is.
  • Help guide treatment decisions.
  • Get a measurement of your CEA level before treatment to compare with CEA levels after treatment.
• During cancer treatment to see if the treatment working.
• After treatment to check whether cancer has come back. You may need to have tests on a regular schedule.

What happens during a CEA test?

CEA is usually measured with a blood sample. 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 other body fluids. For these tests, your provider will remove a small sample of fluid using a thin needle.

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

For a CEA blood test, you usually don't need to prepare. If you smoke, you may need to stop for a while before your test. That's because smoking increases CEA levels.

Are there any risks to the test?

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

What do the results mean?

To understand your CEA test results, your provider will consider the results of other tests and exams. Ask your provider to explain what your test results mean for your health and treatment.

If you had a test before starting cancer treatment, in general:

• A low level of CEA may mean your tumor is small and the cancer has not spread to other parts of your body. But some cancers don't make much CEA, so your provider may use other tests to learn more about how much cancer you have and if it's spread.
• A high level of CEA may mean you have a larger tumor and/or your cancer has spread. You'll need other tests to confirm how serious your cancer is.

If you had a test to monitor your cancer during or after treatment, your provider will compare your current CEA test results with your past test results. In general:

• Decreases in CEA over time often mean that treatment is working.
• Increases in CEA or high levels that stay high may mean that treatment isn't working. For example, if you had surgery for colorectal cancer, these levels may mean that the entire tumor wasn't removed or the cancer is growing back.
• Decreases in CEA after treatment followed by increases may mean cancer has come back.

CEA levels that remain high or increase after treatment don't always mean that treatment isn't working, or cancer is growing. So, if your CEA levels don't come down, your provider will likely order other tests to find out why.

If you have questions about your results, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a CEA test?

Labs use different methods to measure CEA. The test method can affect your results. So, its best to have your tests done the same way, and usually in the same lab. This allows your provider to compare your results over time. If you have questions about how your tests are done, ask your provider.