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Genetic and Biomarker Testing
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Glossary on

testing and genetic testing for people with colorectal cancer

This section covers the following topics:


tests look at samples of tumor, blood or other tissue for changes or abnormalities caused by cancer. These tests can give doctors clues about the cancer, including:

  • how fast the cancer is growing
  • which treatments are most likely to work
  • whether or not the cancer is responding to treatment or growing
  • whether or not the cancer has come back after remission

Biomarkers for treatment selection

tests may be used to select treatments, and help patients avoid side effects from treatments that will not work for them. These tests may be done on tumor tissue or (in some cases) on blood. See our Testing section for more information. 

  • Experts recommend testing all colorectal cancers for an abnormality known as MSI-H (“ high") also known as "" ( or ).
    • and cancers are common in people with a  gene mutation.
    • People with advanced or MSI-high colorectal cancer may respond well to a type of known as an immune checkpoint inhibitor
  • Experts recommend testing  colorectal cancers for the following biomarkers to help guide treatment selection:
    • Mutations in a gene known as RAS (KRAS and NRAS). 
    • A specific mutation in a gene known as BRAF. 
    • (also known as HER2/neu). Tumors that have this are known as
  • Additional tests that may be used in colorectal cancer:
    • A known as an NTRK fusion is rare in colorectal cancer. Advanced/metastatic colorectal cancer with an NTRK fusion may benefit from the Vitrakvi (larotrectinib).
    • Additional tumor testing may help people learn if they are eligible for certain clinical trials. 

Genetic testing for inherited mutations

About 10 percent of colorectal cancers are caused by an . You can find a list of genes associated with colorectal cancer here. Genetic testing can help people with colorectal cancer and their relatives learn more about their cancer risks and medical options. 

Who should get genetic testing?

Genetic testing for hereditary colorectal cancer is recommended in the following situations:

  • colorectal cancer diagnosed at age 50 or younger
  • or MSI-H cancer
  • cancer in people with a personal or family history of other cancers

See our section on genetic testing for a more complete list of who should consider genetic testing. 

Expert Guidelines
Expert Guidelines

The National Comprehensive Cancer Network (NCCN) recommends the following for tumor testing in people with colorectal cancer:

  • All newly-diagnosed colorectal cancers should be tested for  (MSI) or  ( or ).  
    • People diagnosed with advanced MSI-H/dMMR cancers may benefit from treatment with a type of known as immune checkpoint inhibitors.
  • Depending on MMR/MSI test results, people should be referred for genetic counseling for an inherited gene mutation associated with
  • Additional tumor tests may help determine treatment options in  colorectal cancer. This includes testing for:
    • BRAF 
    • KRAS
    • NRAS

Expert Guidelines
Expert Guidelines

The National Comprehensive Cancer Network (NCCN) has guidelines for genetic counseling and testing for people diagnosed with colorectal or endometrial cancer. People who have any of the following should speak with a genetics expert about genetic testing:

  • A tumor test result that suggests an (for example, an MSI-H or tumor). 
  • A blood relative who tested positive for an  linked to cancer.
  • Colorectal or endometrial cancer diagnosed before age 50.
  • Diagnoses of more than one cancer.
  • A family history of one or more first- or second-degree relatives with any of the following types of cancer diagnosed before age 50 or two or more first- or second-degree relatives with any of the following cancers diagnosed at any age:
    • colorectal
    • endometrial
    • ovarian
    • gastric
    • small bowel
    • biliary tract
    • pancreatic
    • urothelial
    • brain (usually glioblastoma)
  • Colorectal cancer and a personal history of polyps:
    • 10 or more adenomatous
    • 2 or more hamartomatous
    • 5 or more serrated close to the rectum

Paying For Care
Paying For Care

Paying for testing

Insurance companies are required to cover the costs for cancer treatment. Health plans may vary on the amount of out-of-pocket costs and coverage for specific doctors, facilities, tests or treatments. Your doctor's office and treating hospital should disclose how much your treatment may cost you and work with you on a plan to cover the cost of your care.

Medicare will cover the cost for genetic testing and testing for people who meet certain criteria. Medicare coverage varies based on where you live. Visit this site to find and contact your regional Medicare provider for more information about coverage. The Medicaid website has a link to state Medicaid programs, which list specific eligibility for each state.

If you need information about finding an insurance plan, watch our video: Choosing Wisely: How to Pick Insurance Plans.Visit our Health Insurance Appeals page for additional information on insurance appeals. 

Some laboratories have assistance programs that help cover the cost for tumor testing: 

Organizations that offer co-pay assistance:

Other resources:

  • The American Cancer Society provides information and resources on covering the cost of cancer care. Public assistance, such as Medicaid may be available if you are ineligible for other programs. 
  • Triage Cancer offers tools and resources to help individuals cope with the financial aspects of a cancer diagnosis.
Last updated November 12, 2023