Doctors want to learn as much as possible about each person’s cancer. That’s why, in some cases, they may recommend tumor marker testing during the various stages of diagnosis, treatment, and follow-up care. Tumor marker tests can provide important information about a cancer and the best way to treat it.

1. What are tumor markers?

Tumor markers are substances found in higher-than-normal levels in the blood, urine, or tissues of some people with cancer. These substances, which are also called biomarkers, can be made by the tumor. They can also be made by healthy cells in response to the tumor. Tumor marker tests check to see if you have these substances in your body and in what amounts. Tumor markers are often proteins. In addition, certain genetic changes are now being used as tumor markers.

2. Why are tumor marker tests used?

Along with other tests, tumor marker tests can help doctors diagnose cancer and recommend a treatment plan for an individual. Why, when, and how often these tests are done varies greatly from person to person. Rarely, they are used to help screen for a particular type of cancer in people with a high risk of the disease before they have signs and symptoms. But doctors mainly use tumor marker tests to:

• Decide which type of treatment or combination of treatments will work best for a certain type of cancer

• Figure out how well a treatment is working

• Predict a person’s chance of recovery

• Predict how likely it is a cancer will come back after treatment and find it if it does

3. Are there different types of tumor markers?

There are different types of tumor markers for different types of cancer. Certain tumor markers are associated with only 1 type of cancer. Other tumor markers are associated with more than 1 cancer. However, many cancers have no known tumor markers, so tumor marker testing may not be an option. Researchers continue to look for new and more effective tumor markers.

4. What’s an example of how tumor marker testing can guide cancer care?

Understanding how tumor markers can affect your treatment choices can be complicated, but asking for examples can help. For instance, early-stage breast cancer has specific tumor markers that can help doctors tailor an individual’s treatment. If a person is diagnosed with this disease, the doctor may test for tumor markers known as estrogen receptor (ER) and progesterone receptor (PR). If the tests are positive for them, her doctor knows that the patient is more likely to be treated successfully with hormone therapy.

If your doctor suggests tumor marker testing, ask which tumor markers you’ll be tested for and how often. Also, ask what the doctor hopes to learn from the testing.

5. What are the limitations of tumor marker tests?

Tumor marker tests can provide a lot of helpful information, but they aren’t fail-safe. Just because a person has tumor markers, it doesn’t always mean cancer is present or has come back. Conditions besides cancer can raise tumor marker levels. Other limitations include:

• Tumor markers can go up and down over time, making it hard to measure them consistently.

• The level of a tumor maker may not go up until after the cancer is advanced.

• Some cancers don’t make tumor markers that can be found with current tests.

• Some people don’t have higher tumor marker levels even if the type of cancer they have usually makes tumor markers.

6.  How are tumor marker tests done?

There are 3 ways your doctor can test for tumor markers: a blood test, a urine test, or a biopsy. A member of your health care team will send a sample of your blood or urine into a laboratory for analysis. If a biopsy is done, a doctor will remove a small amount of tissue that will be examined by a pathologist under a microscope. You may need to repeat your tumor marker tests, because your tumor marker levels can change over time.

7. What do I need to know about tumor marker test results?

There’s a chance that a tumor marker test can give a “false positive.” That means the results suggest a person has cancer or that the cancer is growing, even when it’s not. A tumor marker can also give a “false negative,” which means the results suggest a person doesn’t have cancer when they actually do. Or it can suggest a treatment is working when it’s not. That’s why other diagnostic tests are usually done along with tumor marker tests.

8. Where can I learn more about tumor markers and tumor marker testing?

Ask your doctor to provide general information on tumor markers and tumor marker testing, as well as information specific to your type of cancer. You can also learn about tumor markers in the specific Type of Cancer sections on Cancer.Net. 

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