What is a cancer biomarker and why is it important for cancer treatment?

What is a cancer biomarker?

You might have heard the term ‘cancer biomarker,’ but what does it actually mean and why are cancer biomarkers important for cancer treatment?

A cancer biomarker is a protein, gene or biological molecule that can be detected in the blood or other body fluids to indicate the presence of cancer. Some cancers have biomarkers that are made by the cancer itself (called tumour-associated markers or tumour markers), while other biomarkers are made by your own immune system in response to the presence of cancer.

There are many different types of cancer, with each type having distinct sets of biomarkers associated with them. For example, there are specific biomarkers for breast cancer, prostate cancer, ovarian cancer, bowel cancer and recurrent cancer (cancer which returns). Some biomarkers are associated with only one type of cancer, whereas others are associated with multiple different cancer types.

However, there are some types of cancers that don’t have any known biomarkers.

How are cancer biomarkers used to detect cancer?

Although an elevated level of a circulating tumour marker may suggest the presence of cancer and can sometimes help to diagnose it, this alone is not enough to diagnose cancer. For example, noncancerous conditions can sometimes cause the levels of certain tumour markers to increase.

Not everyone with a particular type of cancer will have a higher level of a tumour marker associated with that cancer. Therefore, measurements of circulating tumour markers are usually combined with the results of other tests, such as biopsies or imaging, to diagnose cancer.

Tumour markers may also be measured periodically during cancer therapy to show how the level of a marker is changing over time. This is usually more meaningful than a single measurement. For example, a decrease in the level of a circulating tumour marker may indicate that the cancer is responding to treatment, whereas an increasing or unchanged level may indicate that the cancer is not responding.

Circulating tumour markers may also be measured periodically after treatment has ended to check for recurrence (the return of cancer).

Circulating tumour markers

Examples of commonly used circulating tumour markers include:

Calcitonin

Measured in blood – which is used to assess treatment response, screen for recurrence, and estimate prognosis in medullary thyroid cancer.

CA-125

Measured in blood – to monitor how well cancer treatments are working and if cancer has come back in ovarian cancer.

Prostate specific antigen (PSA)

May be used as part of screening for prostate cancer and monitoring of patients being treated for prostate cancer.

Biomarker tests

Some of the most common and important biomarker tests used to detect cancer include:

Tissue markers

These are found in the tumours themselves, typically in a sample of the tumour that is removed during a biopsy. The tumour tissue markers are important as they are used to diagnose, stage, and/or classify cancer, estimate prognosis, and select an appropriate treatment.

Tumour tissue markers indicate whether someone is a candidate for a particular targeted therapy and are sometimes referred to as biomarkers for cancer treatment. Examples of tumour tissue markers that are used as biomarkers for cancer treatment are oestrogen receptor and progesterone receptor, which are tested for to determine if someone with breast cancer should get treatment with hormone therapy.

Blood tests

Most of us are familiar with blood tests and in this context they can help your doctor determine if you might have a certain type of cancer. Blood tests can highlight abnormal levels of particular substances in your blood.

For example, a higher-than-normal level of CA19-9 may indicate pancreatic cancer.

Liquid biopsy

Some tumours shed cells and genetic material into blood and it is sometimes possible to examine biomarkers in blood samples. These are called liquid biopsies, and although they are not yet routinely used, they have several potential advantages.

Because they don’t involve surgery, they can be done more frequently than standard biopsies. They can also be performed when surgical biopsies cannot, such as when tumours are difficult to reach, or if a patient can’t tolerate surgery.

Liquid biopsy tests can often detect multiple cancer-associated biomarkers.

Genetic tests

Genetic tests look at the DNA within your cells to see if there are any mutations present that could give you an increased chance of developing certain types of cancer. They can also potentially help doctors understand more about the cancer.

Doctors can look for somatic or acquired gene mutations within the tumour tissue. These are the most common cause of cancer, occurring from damage to genes in an individual cell during a person’s life. This information might help doctors determine the prognosis of the cancer and predict which treatments might be useful to treat it.

Germline mutations or variants are far less common, accounting for only about 5%–10% of all cancers. These types of abnormalities can be detected in a person’s bloods, saliva, tumour tissue and other body tissues. These genetic abnormalities can be inherited. For example, a genetic test may reveal that you have a mutation in the BRCA1 or BRCA2 genes, which can increase your risk of developing breast and ovarian cancer and may also be present in your relatives.

The content on the Icon Cancer Centre website is for informational purposes only and should not be considered medical advice. It is not a substitute for consultation with a qualified medical practitioner. For personalised medical guidance, please consult with your GP or another qualified healthcare provider.