Cancer Treatment: What Are Biomarker Tests?
What are biomarkers?
Cancers are made up of abnormal cells. These cells can produce different types of abnormal substances, called biomarkers (or tumor markers). Biomarkers may be found within or around tumors, in blood, urine and other body fluids. They include:
- proteins.
- genetic material (gene mutations, abnormal chromosomes, or RNA, fused genes).
- cellular material.
What are tests used for?
tests may aid decision-making in different ways:
- Measuring risk for recurrence: Some tests predict how fast a cancer is growing and the risk for recurrence. Examples include OncotypeDX, Mammaprint and Endopredict for breast cancer and OncotypeDX and Prolaris for cancer.
- Monitoring response to treatment, progression or recurrence: These tests often measure changes in biomarkers over time to learn if the cancer is responding to treatment. Examples include CA125 testing to monitor ovarian cancer and testing to monitor cancer.
- Aiding in treatment selection: Some cancer treatments work best in people with certain biomarkers. In these cases, testing can help identify people who are most likely to respond to a particular treatment.
- Detecting cancer: Some tests are being studied to see if they can be used for early detection of cancer.
What type of sample is needed for testing?
The type sample used for a depends on the test being run.
- Most tests are run on a piece of tissue from the tumor obtained by biopsy or surgery. Some tests may be run on stored tumor tissue that was collected and saved at the time of your diagnosis, even if your biopsy was done a while ago. If you have enough tumor tissue stored, using this "archival tissue" may spare you from a new biopsy.
- Some tests require fresh tissue, which means you may need a new biopsy. This is because some tumor biomarkers change over time as cancer cells grow, spread or become resistant to treatments.
- Some tumors may release cells or biomarkers into the blood, urine or other fluids. This provides a more convenient way to find cancer or to monitor response to treatment without the need for a tissue biopsy. These obtained from fluids are called liquid biopsies.
What are liquid biopsies?
Liquid biopsies are tests that look for signs of cancer in blood or other body fluids. Liquid biopsies can be categorized by the type of substances they detect:
- Tests that look for cancer cells in the bloodstream are called Circulating Tumor Cell (CTC) tests.
- Tests that look for fragments from cancer cells are called circulating tumor ( tests).
Liquid biopsies can be categorized by how they are used:
- Treatment selection tests look for biomarkers that guide selection of targeted treatments.
- () tests look for evidence of cancer remaining or recurring after treatment or surgery.
- Single-site tests and (MCD) screen are used for screening and detection of cancer.
Which biomarkers can be used for treatment selection?
Some therapies work best in cancers that have specific biomarkers. tests may be used to select the best to treat a particular cancer. About 100 targeted therapies have approval to treat different types of cancers.
Certain genes are important for repairing damage. These are sometimes referred to as " damage repair" (DDR) genes. Some therapies work best in cancers that have faulty DDR genes. You can read more about tests and treatments for these tumors in the damage repair section below.
DNA damage repair biomarkers
Certain genes are important for repairing damage. These genes are sometimes referred to as " damage repair" (DDR) genes.
- In a normal cell, a mutation in a DDR gene increase the chance that it will become cancer. This is why an in a gene that repairs damage increases the risk for cancer.
- In a cancer cell, a mutation in a DDR gene can keep it from repairing damage caused by treatment. This means that cancer cells with mutations in these genes may be more sensitive to certain treatments.
Two main types of damage repair genes are linked to increased cancer risk and improved response to certain types of treatment:
- "Homologous recombination response" (HRR) genes
- "Mismatch repair" (MMR) genes
Genetic tests can identify people with an in a DDR gene. tests can find tumor cells that have difficulty repairing these types of damage.
HRR and HRD-positive
HRR ( Response) genes repair a type of damage known as "double-stranded damage." Cancers with difficulty repairing this type of damage are known as ( deficient). Cancers that have difficulty repairing this type of damage may respond better to treatment with a type of known as PARP inhibitors.
- Genetic testing for inherited () mutations may help identify people who would benefit from treatment with a . This includes people with advanced breast, ovarian, pancreatic or cancer.
- Tumor testing for acquired (somatic) mutations may help identify people who would benefit from treatment with a . This includes people with advanced ovarian or cancer.
- testing is a special type of test to find tumors that have difficulty repairing double-stranded damage. testing looks for "genomic instability" within tumors, that makes it hard for them to repair damage. Tumors that have this type of genomic instability are sometimes called "HRD-positive." testing can help find ovarian cancers that respond better to PARP inhibitors. testing may also be used to find people who qualify for certain clinical trials.
- HRR testing is a special type of to find tumors that have certain mutations that may make them sensitive to PARP inhibitors. HRR testing can help find cancers that respond better to PARP inhibitors. HRR testing may also be used to find people who qualify for certain clinical trials. HRR testing looks for tumor mutations in the following genes:
MSI-High and ()
Mismatch repair (MMR) genes repair damage that occurs during cell division. Tumors with mutations in mismatch repair genes are called "mismatch repair deficient" (also called or ). These tumors typically have an abnormality known as " high," or MSI-H for short. Mutations in the genes are often associated with and MSI-H tumors.
Testing tumors for dMMR/MMR-D or can be important, because these tumors are more likely to respond to a type of known as immune checkpoint inhibitors.
Tumor testing vs. genetic testing
Tumor tests look for gene mutations in cancer cells. These tests differ from genetic tests for risk.
As cells become cancerous, they develop many gene mutations that cause abnormal growth. These gene changes, which occur after you are born and throughout your life—are known as acquired or "somatic" mutations. Acquired mutations are different than inherited mutations, which are passed on from parent to child and are present at birth in every cell.
As cells become cancerous, they develop many gene mutations that cause abnormal growth. These gene changes, which occur after you are born and throughout your life—are known as acquired or "somatic" mutations. Acquired mutations are different than inherited mutations, which are passed on from parent to child and are present at birth in every cell.
Tumor tests can look for mutations in cancer cells. Genetic tests for inherited mutations look at normal cells in blood or saliva to find gene changes that are present from birth, passed from parents to children and are linked to increased risk for .
Information provided by tumor testing and genetic testing may overlap. If a person is born with a genetic mutation and later develops cancer, that mutation may show up when the tumor is tested. This is because the cancer grew from the person’s own cells. For example, someone born with a mutation has that mutation in all of their cells. If they develop cancer, the cancer cells will usually have the same mutation. Similarly, if a person is born with an inherited mutation and develops colorectal cancer, the tumor will often show the same mutation and may also have features such as high (MSI‑High).
Not all tumor tests can distinguish inherited mutations from acquired mutations. If your shows a mutation, ask your doctor if it may be hereditary and if you should have genetic testing for an .
Common biomarkers used for treatment selection
The following biomarkers may be used to select treatment for cancer. This is not a complete list of all biomarkers and available treatments. Additional biomarkers may be used to for clinical research studies. Speak with your doctor about additional testing which may help guide your treatment.
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Questions for your doctor
Below are some questions to ask your doctor about testing:
- Has my tumor been testing for biomarkers? If so, what were the results?
- Is there a that might be more effective for my cancer? If so, will I need a tissue biopsy or is a an option?
- How will you monitor my cancer for recurrence?
- Are there liquid biopsies that can tell if my cancer has recurred?