What are they?

Tumour markers are substances, usually proteins, that are produced by the body in response to cancer growth or by the cancer tissue itself. Some tumour markers are specific for one type of cancer, while others are seen in several cancer types. Many of the well-known markers are seen in non-cancerous conditions as well as cancer. Consequently, they cannot be used to diagnose cancer.

There are only a handful of well-established tumour markers that are being routinely used by doctors. Many other potential markers are still being researched. Some marker tests cause great excitement when they are first discovered but, upon further investigation, prove to be no more useful than markers already in use.

The goal is to be able to screen for and diagnose cancer early, when it is the most treatable and before it has had a chance to grow and spread. So far, no tumour marker has gained acceptance in Australia as a general screen, including the prostate specific antigen (PSA) for men. The markers are either not specific enough (too many false positives, leading to expensive and unnecessary follow-up testing) or they are not elevated early enough in the disease process.

In 1968 the World Health Organization recommended ten principles to be followed when countries consider developing national screening programs. The essence of these is that the disease should be important, well understood and be able to be recognised and tested for at an early stage. Medical support and treatment must be available and be more beneficial if given at an early stage. The health benefits must be greater than any harm done by the screening process which also must be cost effective.

Some people are at a higher risk for particular cancers because they have inherited a genetic mutation. While not considered tumour markers, there are tests that look for these mutations in order to estimate the risk of developing a particular type of cancer. BRCA1 and BRCA2 are examples of gene mutations related to an inherited risk of breast cancer and ovarian cancer.

Why are they done?

Tumour markers are not diagnostic in themselves. A definitive diagnosis of cancer is made by looking at biopsy specimens (e.g., of tissue) under a microscope. However, tumour markers provide information that can be used to:

• Monitor. While at present no markers are suited for general screening, some may be used to monitor those with a strong family history of a particular cancer. In the case of genetic markers, they may be used to help predict risk in family members.
• Help diagnose. In a patient that has symptoms, tumour markers may be used to help identify the source of the cancer, such as CA-125 for ovarian cancer, and to help differentiate it from other conditions. Remember that tumour markers cannot diagnose cancer themselves but aid in this process.
• Stage. If a patient does have cancer, tumour marker elevations can be used to help determine how far the cancer has spread into other tissues and organs.
• Determine prognosis. Some tumour markers can be used to help doctors determine how aggressive a cancer is likely to be.
• Guide treatment. Some tumour markers, such as Her2/neu, will give doctors information about what treatment their patients may respond to (for instance, breast cancer patients who are Her2/neu positive are more likely to respond to Herceptin therapeutic drug treatment).
• Monitor treatment. Tumour markers can be used to monitor the effectiveness of treatment, especially in advanced cancers. If the marker level drops, the treatment is working; if it stays elevated, adjustments are needed. The information must be used with care, however. Carcinoembryonic antigen (CEA), for instance, is used to monitor bowel cancer, but not every bowel cancer patient will have elevated levels of CEA. If the marker level is not initially elevated with the cancer, it cannot be used later as a monitoring tool.
• Determine recurrence. Currently, one of the biggest uses for tumour markers is to monitor for cancer recurrence. If a tumour marker is elevated before treatment, low after treatment and then begins to rise over time, then it is likely that the cancer is returning. (If it remains elevated after surgery, then chances are that not all of the cancer was removed.)

Common tumour markers currently in use

tumour markers	cancers	What else?	When/how used	Usual sample
Alpha-fetoprotein (AFP)	Liver, germ cell cell cancer of ovaries or testes	Also elevated during pregnancy	Help diagnose, monitor treatment, and determine recurrence	Blood
CA 15-3 (Cancer antigen 15-3)	Breast cancer and others, including lung, ovarian	Also elevated in benign breast conditions	Stage disease, monitor treatment, and determine recurrence	Blood
CA 19-9 (Cancer antigen 19-9)	Pancreatic, sometimes bowel and bile ducts	Also elevated in pancreatitis and inflammatory bowel disease	Stage disease, monitor treatment, and determine recurrence	Blood
CA-125 (Cancer antigen 125)	Ovarian	Also elevated with endometriosis, some other benign diseases and conditions; not recommended as a general screen	Help diagnose, monitor treatment, and determine recurrence	Blood
Calcitonin	Medullary thyroid carcinoma	Also elevated in pernicious anaemia and thyroiditis	Help diagnose, monitor treatment, and determine recurrence	Blood
Carcinoembryonic antigen (CEA)	bowel, lung, breast, thyroid, pancreatic, liver, cervix, and bladder	Elevated in other conditions such as hepatitis, COPD, colitis, pancreatitis, and in cigarette smokers	Monitor treatment and determine recurrence	Blood
hCG (Human chorionic gonadotropin)	Testicular and trophoblastic disease	Elevated in pregnancy, testicular failure	Help diagnose, monitor treatment, and determine recurrence	Blood, urine
Her-2/neu	Breast	Oncogene that is present in multiple copies in 20-30% of invasive breast cancer	Determine prognosis and guide treatment	Tissue
Monoclonal immunoglobulins	Multiple myeloma and Waldenstrom’s macroglobulinaemia	Overproduction of an immunoglobulin or antibody, usually detected by protein electrophoresis	Help diagnose, monitor treatment, and determine recurrence	Blood, urine
Oestrogen receptors	Breast	Increased in hormone-dependent cancer	Determine prognosis and guide treatment	Tissue
Progesterone receptors	Breast	Increased in hormone-dependent cancer	Determine prognosis and guide treatment	Tissue
PSA (Prostate specific antigen)	Prostate	Elevated in benign prostatic hyperplasia, prostatitis and with age	Screen for and help diagnose, monitor treatment, and determine recurrence	Blood
Thyroglobulin	Thyroid	Used after thyroid is removed to evaluate treatment	Determine recurrence	Blood
Other Tumor Markers Less Widely Used
B2M (Beta-2-microglobulin)	Multiple myeloma and lymphomas	Present in many other conditions, including Crohn’s disease and hepatitis.	Determine prognosis	Blood
NSE (Neuron-specific enolase)	Neuroblastoma, small cell lung cancer	May be better than CEA for following this particular kind of lung cancer	Monitor treatment	Blood
Soluble mesothelin-related peptides (SMRP)	Mesothelioma	Often used in conjunction with imaging tests	To monitor progression or recurrence	Blood

 

Links

Macmillan Cancer Support (UK)
National Cancer Institute (US): Tumor Markers
 

Additional information: Sources

 

Last Review Date: January 11, 2023

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