A tumor marker is a substance found in your blood, urine, or body tissue. The term "tumor markers" may refer to proteins that are made by both healthy cells and cancer cells in the body. It may also refer to mutations, changes, or patterns in a tumor's DNA. Tumor markers are also called biomarkers.
Doctors may use tumor marker tests to learn if you have cancer. These tests can also help doctors to learn more about your cancer and help to plan treatment.
How are tumor marker tests used?
High tumor marker levels can be a sign of cancer. Along with other tests, tumor marker tests can help doctors diagnose specific types of cancer and plan treatment. Tumor marker tests are most commonly used to do the following:
Learn if a person has cancer. Higher tumor marker levels may indicate a certain type of cancer. A tumor marker test may be used as a part of your initial diagnosis.
Check the progress of treatment. Changes in your tumor marker levels can show how well the treatment is working.
Predict the chance of recovery. Tumor markers can help doctors predict the cancer's behavior and response to treatment. They can also predict your chance of recovery.
Predict or watch for recurrence. Recurrence is when cancer comes back after treatment. Tumor marker tests can help predict how likely this is. That's why these tests might be part of your care after treatment ends. They may help find a recurrence sooner than other tests.
Tumor marker tests may also be used to look for cancer in people with a high risk of the disease. Or you might have these tests to learn more about the cancer when doctors first find it.
Limits of tumor marker tests
Tumor marker tests are not perfect. They are often not specific for cancer and may not be sensitive enough to pick up a cancer recurrence. The presence of tumor markers alone is not enough to diagnose cancer. You will probably need other tests to learn more about a possible cancer or recurrence. Some limits to tumor marker tests are listed below.
A condition or disease that is not cancer can raise tumor marker levels.
People without cancer can have high tumor marker levels.
Tumor marker levels can change over time. The tests may not get the same result every time.
Tumor marker levels may not go up until cancer gets worse. This does not help find cancer early, or in people at high risk. It also does not help find a recurrence.
Some cancers do not make tumor markers that are found in the blood. And, some types of cancer have no known tumor markers.
Your tumor marker levels might not go up, even if your type of cancer usually makes tumor markers.
How is a tumor marker test done?
A member of your health care team will take a sample of your blood or urine. The sample goes to a laboratory for testing. Some tests must be done more than once, because the levels of tumor markers can change regularly.
You will also need other tests to find cancer and check on treatment. This is because tumor marker results have limitations (see above) and are sometimes wrong. They might:
Show a tumor is present or growing when it is not.
Show there is no tumor when one is present, or show treatment is working when it is not.
No test is perfect. So your doctor will probably order several types of tests to find answers.
Tumor marker tests and specific cancers
Doctors use different tumor marker tests for different cancers. However, many cancers do not yet have tumor markers that can help guide care.
Ask your health care team if you will have tumor marker testing. You can also find information on tumor markers in the sections on different cancers on Cancer.Net.
Questions to ask the health care team
You might want to ask your health care team these questions.
Do you think I need any tumor marker tests? Which ones, and why?
Have you looked for tumor markers already? Which ones?
How are these tests done? How often should I have them?
Who can explain the results to me?
If I have abnormal levels of a tumor marker, what does that mean? How could this result affect my treatment plan?
Will I need tumor marker tests after my cancer treatment ends?
Where can I learn more about tumor markers and testing?