Your body is full of information that can give you a clearer picture of what’s going on inside it. Sometimes you just need the right translation book to understand what it’s trying to tell you. In cancer, biomarkers (short for biological markers) can be this translator.
Biomarkers are useful tools to help you and your medical team understand your diagnosis, gene makeup, and treatment options. Read on to learn what biomarkers are and how they can be helpful if you have been diagnosed with colorectal cancer, also known as colon cancer.
What are biomarkers?
Biomarkers are molecules in body fluids or tissues that can be measured to indicate whether the body has a particular disease or how effectively it is responding to treatment.
There are seven types of biomarkers:
- Susceptibility/risk biomarkers – Predict how likely you are to develop a particular condition
- Diagnostic biomarkers — recognize or confirm a condition
- Prognostic biomarkers – predict the likelihood that a condition will worsen or recur
- Monitor biomarkers — Determine the status of a disease or the body’s response to treatment
- Predictive biomarkers – help predict whether a person would respond well to certain treatments
- Biomarkers of pharmacodynamic response — show how the body responded to treatments
- Safety biomarkers — Determine the level of toxicity in the body after treatment
Who needs biomarker testing?
Some biomarkers are used in routine tests, such as your blood pressure. Other types of biomarker tests may be helpful for people with certain diseases, including cancer. Because cancer varies from person to person at the gene or protein level, biomarker testing helps healthcare providers (HCPs) create a personalized treatment plan that targets your specific tumor. Your HCP can help you decide whether biomarker testing is right for you.
How are biomarkers tested?
For cancer patients, biomarker testing is performed by taking samples of cancer cells. This can be done by taking a sample of tissue or cells from the tumor (called a biopsy), a blood sample or fluid biopsy, a bone marrow sample, or a sample of other body fluids such as urine or saliva.
Samples of your healthy cells are also sometimes taken for biomarker testing to compare between healthy cells and cancer cells.
What types of biomarkers are tested for colorectal cancer and when should the tests be done?
There are four common types of predictive biomarkers in colorectal cancer:
People with stage 4 colon cancer should be tested for at least these biomarkers at initial diagnosis to determine the most effective treatment options.
People with colorectal cancer should also be tested for high microsatellite instability (MSI-H). In most cases, this mutation is not hereditary. But in a small percentage of people, this genetic mutation is passed down through your genes and can be caused by Lynch syndrome. Lynch syndrome can increase your risk of many types of cancer.
During treatment, testing for prognostic biomarkers such as carcinoembryonic antigen (CEA) can help determine how well the treatment is working and whether relapses occur.
If the cancer comes back, biomarker tests should be done to determine how well the body is responding to new treatments and whether the cancer has spread.
What are the most common colorectal biomarkers?
MSI-H: About 15 out of 100 of all colorectal cancers and about 4 out of 100 stage 4 colorectal cancers have an MSI-H mutation. Surgery and immunotherapy are usually the preferred treatment options for this type of tumor.
KRAS: A mutated KRAS protein can cause uncontrollable cell growth and lead to cancer. About 2 in 5 colon cancer tumors have a KRAS mutation. Chemotherapy and other targeted treatments are usually the most effective options for a person with a KRAS mutation.
NRAS: Similar to KRAS mutations, NRAS mutations can cause uncontrollable cell growth and lead to cancer. NRAS mutations only occur in about 3 to 5 out of 100 colon cancer tumors. Chemotherapy and other targeted treatments are usually the best options for people with an NRAS mutation.
BRAF: Like KRAS and NRAS, BRAF mutations can cause uncontrollable cell growth and lead to cancer. A BRAF mutation typically means the cancer is aggressive and may be at a later stage. For people with a BRAF mutation, chemotherapy, other targeted treatments, or a combination of treatments may be recommended.
HER2: The HER2 biomarker measures the amount of HER2 protein released. HER2 positive means too much protein is released, which can lead to uncontrolled cell growth and cancer. HER2-positive cancers are more common in people who do not have KRAS, NRAS, or BRAF mutations. Treatment of cancer with a HER2-positive biomarker is typically through anti-HER2 therapies, sometimes called HER2 inhibitors.
CEA: The gastrointestinal tract releases CEA into the blood. Colon cancer cells can also release CEA into the blood. Because healthy adults typically have low CEA levels, test results that show high levels may mean that a large tumor is present or that the cancer has spread to other places in the body.
While these are some of the most common biomarker tests for colorectal cancer, there may also be other biomarker tests that your doctor may recommend.
Are biomarker tests covered by insurance?
Whether biomarker testing is covered by insurance varies from plan to plan and state to state. Currently, 18 states have mandatory biomarker testing coverage laws for state-regulated plans. Several more states are introducing legislation this year.
Talk to your HCP about what types of biomarker tests you may need and contact your insurer to find out if your tests are covered.
This educational resource was created with support from Merck.
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