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What is a biomarker?

Biomarkers, short for biological markers, are molecules found in blood, tissue, or other bodily fluids that can be measured and provide information about your tumor’s characteristics. Your “biomarker profile” can help your doctor and medical team personalize your treatment based on:

  • What changes drive tumor growth (a driver mutation)

  • The likely outcome of a cancer if it is left untreated (prognosis)

  • The likelihood that a specific treatment plan will work (predictive)

  • The likelihood of severe toxicity to certain treatments (predictive))

  • The likelihood that the tumor will come back (tumor recurrence)

Biomarkers 101

Learn the basics about biomarkers so that you are fully informed on your journey.

What is biomarker testing?

After you discuss biomarker testing, a sample of your tumor (tissue biopsy) or your blood (liquid biopsy) will be collected at your doctor’s office. The sample will be sent to a certified pathology laboratory in your medical facility or to an external diagnostic laboratory.

One or more tests will be done to show the changes in the DNA, RNA, or proteins that happened in your cancer cells. Tests can be limited to only a few genes or proteins or many genes at once using new, comprehensive techniques such as NGS (New Generation Sequencing) and multi-gene panels. With new technology, many different testing platforms can now be used for biomarker testing. There are advantages and disadvantages to each one of the tests. You should discuss these with your doctor.

Once testing is complete, ask your doctor for the report and discuss a personalized treatment plan and road-map for your journey.

Why is biomarker testing important?

Knowing your biomarker status will help to identify the unique characteristics of your tumor (for example, whether your tumor has a germline mutation or somatic mutations). Knowing your biomarkers will also help you and your doctor decide on the most effective treatment plan, while avoiding treatments that may not work for you or may cause you harm.

Patient Perspective

Here from a colorectal cancer patient about how her biomarker knowledge informed her journey.

When and how should I have biomarker testing?

Depending on the biomarkers to be tested, the testing could be done at different points in your journey:

The National Comprehensive Cancer Network (NCCN) and American Society of Clinical Oncologists (ASCO) recommend that doctors test these biomarkers individually or as part of comprehensive biomarker testing. These comprehensive, multi-gene panels currently test hundreds of genes at one time.

Download: Biomarkers and colorectal cancer

Information on what is a biomarker, why testing is important and how it is performed.

Download English

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