What are tumor marker tests?
Tumor markers are substances (usually proteins but maybe other substances) that are present in or produced by, cancer cells, or other cells of the body in response to cancer or certain benign (that is non-cancerous) conditions, which provides information about cancer, such as how aggressive it is, whether or not it can be treated with targeted therapy, or whether or not it is responding to treatment. Some tumor markers are specifically for one cancer type, while some tumor markers can be seen in several cancer types. Most recognized tumor markers are also seen in non-cancerous conditions. As a result, they cannot be used in cancer diagnosis.
Tumour marker tests look for tumor markers (which can also be referred to as cancer markers) in the blood, stool, urine, tumors, or body tissues in patients with cancer.
However, while many different tumor markers have been characterized and are in use clinically. There’s no single universal tumor marker that has been found, which can reveal the presence of any type of cancer. Also, tumor marker tests are only carried out on people already diagnosed with cancer.
What are they used for?
It should be clear that tumor marker tests are not diagnostic in themselves. However, tumor markers, or cancer marker as it’s also known, provide useful information that can be used to:
- Monitor: Cancer markers are used to monitor people with a very strong family history of particular cancer or help predict risk in family members.
- Aid in diagnosis: Cancer markers can be used to help identify the source of cancer, and help differentiate it from other conditions.
- Stage: In people with cancer, tumor marker elevations help to determine how far cancer has spread into other tissues and organs.
- Determine prognosis: Some markers help in determining how aggressive a cancer is likely to be.
- Guide treatment: Some cancer markers provide useful tips to doctors about what treatment type their patients may best respond to.
- Monitor treatment: Tumour markers help to monitor the efficiency of treatment, especially in advanced stages of cancer. A drop in the marker level signifies that treatment is working. Continuous or maintained elevation means adjustments are needed.
Why do I need a tumor marker test?
Tumour marker tests are usually requested for three categories of people
- A person currently undergoing cancer treatment.
- A person who just finished cancer treatment.
- A person at high risk of cancer. Either because of family history or other reasons.
The choice of tumor marker test, however, depends on current health status, health history, and symptoms being displayed.
Tumor markers list commonly in use
- Alpha-fetoprotein (AFP tumor marker): For cancer of ovaries or testes and liver cancer. Carried out with a blood sample.
- Cancer antigen 15-3 (CA 15-3): For breast cancer, lungs, and ovarian cancers. Carried out with a blood sample.
- Cancer antigen 19-9 (CA 19-9): For pancreatic, and sometimes bowel and bile duct cancer. Carried out with a blood sample.
- Cancer antigen 125 (CA-125): For ovarian cancer. Carried out with a blood sample.
- Carcinoembryonic antigen (CEA tumor marker): For cancers of the bowel, lung, breast, thyroid, pancreatic, liver, cervix, and bladder. Carried out with a blood sample. Also referred to as CEA testing.
- Human chorionic gonadotropin (hCG): Testicular and trophoblastic disease. Carried out with a blood or urine sample.
- Her-2/neu: For breast cancer. Carried out with a tissue sample.
- Prostate-specific antigen (PSA): For prostate cancer. Carried out with a tissue sample.
- Oestrogen and progesterone receptors: For breast cancer. Carried out with a tissue sample.
What happens during the tumor marker test?
Tumour marker tests may be carried out in different ways.
- Tumor marker blood tests. Which happens to be the most common of tumor marker tests.
- Tumor marker urine tests.
- Biopsies – A minor procedure that involves removing a small piece of tissue, through cutting or scraping the skin, for testing. Sometimes, it involves the use of tissues from inside the body.
What do the results of tumor marker tests mean?
Depending on the tumor marker test you had done and how it was used, the results;
- Help to diagnose the type or the stage of cancer.
- Help to know the effectiveness of cancer treatment.
- Help in planning future cancer treatment.
- Help to know if the cancer is gone or has returned after going through treatment.
Tumour marker test results should also be combined with:
- A thorough review of medical history.
- Physical examination.
- Other laboratory tests.
- Imaging tests.
To ensure accurate diagnosis, as tumor marker tests are not enough to diagnose or screen for cancer.
Will I need anything to prepare for a tumor marker test?
There’s usually no need for any special preparations for a blood or urine cancer marker test. However, for a biopsy, fasting (not eat or drink) may be required before the procedure.
Is there any risk to tumor marker tests?
There is very little risk associated with a tumor marker blood test. Usually, slight pain or bruising may be experienced at the spot where the needle was inserted, but most symptoms quickly go away.
As for a tumor marker urine test, there is no risk associated with it.
For tumor marker biopsy, however, a little bruising or bleeding may occur at the biopsy site. A little discomfort may also be experienced at the tumor marker biopsy site for a day or two.
What are the limitations to tumor marker tests?
As highly useful as tumor marker tests are, they do have certain limitations
- Many tumor markers show elevated levels in persons with conditions or diseases other than cancer.
- Not all who have particular cancer will have an elevated level corresponding to the tumor marker.
- Not all cancer has a tumor marker that has been acknowledged as associated with it.
- Tumor markers results can fluctuate, thereby making consistent measurement hard.
- Some tumor markers only show elevated levels when cancer has advanced.
- Some cancers don’t produce tumor markers that can be found with current tumor marker tests.
- Some people may not show high tumor marker levels even if cancer they have usually produce tumor markers.
Are tumor marker tests accurate?
There is no substantive evidence to prove a 100% reliability on tumor markers in determining the presence or absence of cancer. Also, other health issues or diseases can contribute to raising tumor marker levels.
What does it mean when the result says your tumor markers are high?
High levels of a tumor marker can be a sign of cancer.