Tumour marker tests

Tumour markers are substances (mostly proteins) that are made by cancer cells or by healthy cells in response to cancer. Most of these substances are in our bodies already. But their levels can increase when cancer is present. Some non-cancerous (benign) tumours or conditions can also increase tumour marker levels.

A tumour marker test measures the level of a specific tumour marker in the body. This test can help doctors diagnose cancer, plan treatment and check if treatments are working.

Tumour marker tests may also be called biomarker tests or cancer marker tests.

A tumour marker test may be done to:

• help diagnose a specific type of cancer
• look for a certain type of cancer in people who have an increased risk but don’t have any symptoms (screening)
• see how far the cancer has spread (staging)
• predict how aggressive the cancer is likely to be
• predict what treatment the cancer is likely to respond to
• predict how likely it is that the cancer will come back (recur) after treatment
• check how well cancer treatment is working
• find out if cancer has come back after treatment

There are many types of tumour markers. Some are specific to one type of cancer, while others may be increased with different types of cancer. Some cancers don’t have any known tumour markers.

The following are some common tumour markers that doctors will test for when diagnosing or treating certain types of cancer:

• alpha-fetoprotein (AFP)
• cancer antigen 125 (CA125)
• cancer antigen 15-3 (CA15-3)
• carbohydrate antigen 19-9 (CA19-9)
• carcinoembryonic antigen (CEA)
• human chorionic gonadotropin (hCG or beta-hCG)
• human epidermal growth factor receptor 2 (HER2)
• prostate-specific antigen (PSA)

A tumour marker test is done in a lab or hospital. You usually don’t need to do anything to prepare for these tests.

Most tumour markers are found in blood or urine. They can also be found in body tissues. Samples of blood, urine and body tissues are collected in different ways.

For a blood chemistry test, a lab technologist will take a sample of your blood from a vein in the arm.

If you need a urine test (urinalysis) , the technologist will ask you to collect urine in a clean container.

You may need a biopsy to collect a tissue sample. Depending on where the biopsy is done and how much tissue is taken, you may have a local or general anesthetic. Your doctor will use a special needle or other instrument to collect the sample.

The sample of blood, urine or tissue is sent to a lab to be analyzed by special machines.

You may need to provide blood, urine or tissue samples several times. Doing tumour marker tests over a period of time (called serial measurements) allows your healthcare team to check if cancer treatment is working, if cancer is growing or if the cancer has come back.

Talk to your healthcare team about the results of a tumour marker test and what they mean to you. They can explain how they use tumour marker levels and the results of other tests and procedures to decide on a diagnosis and treatment plan.

If a tumour marker is present or the level is higher than normal, it may mean that there is a non-cancerous tumour or condition in the body. Or it could mean that cancer is present. Your doctor will take a thorough medical history and will need to do other tests to confirm a diagnosis, including:

• a physical exam
• other lab tests
• imaging tests, such as MRI and CT scan

If your healthcare team is using a tumour marker test to check if cancer treatment is working, they will compare the tumour marker’s levels before, during and after treatment.

• If a tumour marker level decreases or returns to normal, it may mean that a treatment is working.
• If a tumour marker level increases, it may mean the cancer is not responding to treatment, is growing or has recurred. But a slight increase may not be significant. So your doctor will look at how the level changes over time to decide what the results mean.

Keep the following in mind when you talk to your healthcare team about tumour marker tests:

• A tumour marker test alone may not identify a specific type of cancer. Some markers are related to different cancers. Some cancers don’t have known markers.
• Tumour marker levels don’t always increase when there is cancer. Some people don’t have high levels even if the type of cancer they have usually makes a specific tumour marker.
• Tumour marker levels may not increase until cancer grows or spreads. This means that a tumour marker test may be less helpful for finding cancer early or knowing if cancer has come back after treatment.
• Tumour marker levels can increase for a short time after treatment. This happens because treatment kills many cancer cells at the same time and they release large amounts of the tumour marker when they die.