A biomarker is a biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease*. A biomarker may be used to see how well the body responds to a treatment for a disease or condition. Biomarkers include important information about your tumor.   


You may hear biomarkers described as “an expression of your tumor”, “tumor type” or “tumor mutation”. Biomarkers are typically either a protein or molecule released by the tumor, or they could be the body’s response to the presence of cancer.

Biomarkers can be identified in DNA, RNA, or proteins. Biomarkers may be a change that occurs in your cancer cells, which is a somatic mutation, and not passed on to offspring.  95% of colorectal cancers are due to somatic mutations.  Unlike somatic mutations, a germline mutation is hereditary.  Because germline mutations can be passed on to offspring, it is important to know your biomarker status and discuss with medical professionals how your results may impact family members.  5% of colorectal cancers are hereditary, or due to germline mutations.




Biomarker testing is done by analyzing biopsies to identify gene mutations.  Molecules may be obtained from your blood, body fluids, or tissue. After a biopsy is taken, a pathologist analyzes it and looks for abnormalities, then reports back to your medical team.

The type of test(s) that you will receive can be limited to a few genes or could be a multi-gene panel test or NGS (Next Generation Sequencing).  Discuss with your medical team what tests you should receive and the benefits or any drawbacks to those tests.



Results from biomarker testing can be predictive or prognostic. Predictive results provide information on the potential effects of targeted therapies or the likelihood of toxicity to treatment. Prognosis results provide information on the potential overall outcome of the cancer diagnosis.


Biomarker testing can provide your medical team with vital personalized information, which can be used to:

  • Gain a better understanding of the prognosis of your cancer diagnosis

  • Help predict how your cancer may or may not respond to a particular treatment

  • Guide treatment decisions

  • Anticipate a potential toxic response to treatment

  • Monitor cancer for reoccurrence


Biomarker tests may also be used to screen for cancer in people with a high risk of the disease. Some may be done to learn more about cancer when it is first diagnosed. However, the presence or amount of a biomarker alone is not enough to diagnose cancer.



​Individuals who have been diagnosed with stage IV or metastatic colorectal cancer should be tested for several biomarkers: RAS (both KRAS and NRAS), BRAF, and HER2.    As science continues to evolve and new treatments are developed for specific biomarkers, testing recommendations should be expanded. 


All colorectal cancer patients, no matter what stage their colorectal cancer was diagnosed, should be tested for Microsatellite Instability.


Dr. Janet Woodcock, Director of the FDA’s Center for Drug Evaluation and Research (CDER), describes what biomarkers are and why they are important to the drug development process. 


Have I had my biomarkers tested?

If so, what do my results mean to my treatment plan?

If not, will my tumor be tested? When should I receive my testing?

What should I be tested for?

How does biomarker testing work?

How long will it take to get my results?

Biomarkers play a critical role in improving the drug development process.


Ongoing research and clinical studies have continued to provide valuable information on biomarkers.

The Global Colon Cancer Association maintains an updated list of common colorectal cancer biomarkers.

Global Colon Cancer Association

The voice for the millions of colon cancer patients worldwide.


Colorectal Cancer Alliance

Raising awareness of preventive measures; providing support for patients, caregivers, and survivors; inspiring the efforts that fund critical research—all to end colorectal cancer in our lifetime.

Fight Colorectal Cancer

Knowing your colorectal cancer biomarkers can help your doctors identify your best treatment options and help you in making well-informed decisions about how your cancer will be treated.


American Society of Clinical Oncology (ASCO) Guidelines

Guidelines to assist medical practitioners to make clinical decisions.

National Cancer Institute (NCI)

Overview of tumor markers.


National Comprehensive Cancer Network (NCCN) 

Explanation of biomarker testing at the center of personalized medicine.


Clinical and academic articles, theses, books, abstracts on colorectal cancer and biomarkers.


Clinical Trials

Clinical trial studies for colorectal cancer and biomarkers.



A Service of National Center for Biotechnology InformationU.S. National Library of Medicine

Citations for biomedical literature from MEDLINE, life science journals, and online books on colorectal cancer and biomarkers. 


The contents of the Know Your Biomarker website, such as text, graphics, images, and other material contained within are for informational purposes only. The content and resources are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition. 

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