Tumor markers

A tumor marker is an important tool used by your care team to learn more about your health.

What are tumor markers?

A tumor marker is a substance found in your body produced by either cancer cells or healthy cells in response to cancer.

Tumor markers are sometimes called cancer markers or biomarkers. They provide important information about your cancer, such as:

• Which treatment may work best
• Whether the current treatment is working
• How aggressive the cancer type is

These cancer biomarkers can be found in body tissue (via a biopsy), blood and urine.

Some biomarkers are specific to one type of cancer, while others are related to several cancers. If your care team is planning to do a tumor marker test, this guide may help you learn more about the procedure.

Tumor marker tests in cancer diagnosis and treatment

Though tumor marker tests are a useful tool for making a diagnosis and planning and monitoring treatment, they aren’t used as a general population-based screening tool. That’s because some tumor markers may be present in noncancerous health conditions.

Below are some of the most common uses for tumor marker tests.

Making a cancer diagnosis: Biomarker testing is sometimes the first step in a cancer diagnosis. It typically isn't used alone to diagnose cancer, but may be among tools used when a doctor suspects cancer.

Making treatment decisions: Biomarker testing can help doctors decide which type of treatment may work best for your cancer type. They’re also helpful in gauging the chances of recovery.

Monitoring current treatment: Regular tumor marker testing during ongoing cancer treatment may help show doctors how the cancer is responding to treatment.

Finding recurrent cancer: Cancer that comes back after treatment is known as recurrent cancer. After cancer treatment has finished, your medical team may recommend regular tumor marker testing to make sure the cancer hasn’t returned.

Your care team will explain why they’re performing the test, but always ask if you have any questions about why a medical test is being ordered or what it might mean for your treatment.

Limitations of tumor marker tests

It’s important to remember a tumor marker alone isn’t enough to diagnose cancer—instead, it gives an indication that additional testing is needed.

Some of the limitations of tumor markers include:

• Not all cancer types have an appropriate tumor marker test.
• Sometimes, patients without cancer can have elevated tumor marker levels. Some noncancerous health conditions also cause high levels.
• Cancer biomarkers can fluctuate over time, which means repeated testing may not give consistent results.
• In some patients, tumor marker levels don’t go up until the cancer has gotten worse, which can make it harder to diagnose cancer or recurrent cancer in its early stages.

If you have concerns about your tumor marker test results, be sure to discuss them with your care team.

Types of tumor markers

There are many different types of tumor markers used in medical treatment and diagnosis. Below is a guide to some of the most commonly used cancer biomarkers.

Alpha-fetoprotein (AFP)

Cancer type: Cancers of the liver, testicles and ovaries

Uses:

• Liver cancer diagnosis
• Cancer staging
• Monitor ongoing treatment

Beta-2 microglobulin (B2M)

Cancer type: Multiple myeloma and some types of leukemia and lymphoma

Uses: Monitor ongoing treatment 

Cancer antigen 15-3 (CA 15-3) and Cancer antigen 27-29 (CA 27-29)

Cancer type: Breast cancer

Uses: Monitor ongoing treatment 

Cancer antigen 125 (CA-125)

Cancer type: Ovarian cancer

Uses: Monitor ongoing treatment and look for recurrence

Carcinoembryonic antigen (CEA)

Cancer type: Mainly colorectal cancer, but sometimes other cancers, including stomach, lung, thyroid and ovary

Uses: Monitor ongoing treatment and look for recurrence

Prostate-specific antigen (PSA)

Cancer type: Prostate cancer

Uses: 

• Screen for prostate cancer 
• Monitor ongoing treatment and look for recurrence