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.
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:
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 suggesting 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.
- diagnosed with more than one cancer.
- a family history of one or more first or with any of the following types of cancer diagnosed before age 50 or two or more first or with any of the following cancers diagnosed at any age:
- small bowel
- biliary tract
- brain (usually glioblastoma)
- colorectal cancer and a personal history of polyps:
- 10 or more of the adenomatous type
- 2 or more of the hamartomatous type
- 5 or more of the serrated type close to the rectum