From the Guidelines
Genetic testing is advised in colorectal cancer for individuals with a known mutation in the family, those diagnosed with colorectal cancer before age 50, or those with specific tumor characteristics suggesting hereditary syndromes, as recommended by the NCCN guidelines 1.
Key Indications for Genetic Testing
- A known mutation in the family
- An individual with colorectal cancer and more than 10 adenomas
- An individual affected with colorectal or endometrial cancer with one or more of the following:
- Diagnosed before age 50
- MSI-high or immunohistochemical staining showing the absence of one or more mismatch repair proteins
- Synchronous or metachronous Lynch syndrome-related cancers
- Classical familial adenomatous polyposis (FAP)
- A first-degree relative with colorectal or endometrial cancer diagnosed before age 50
- A first-degree relative with colorectal or endometrial cancer and another synchronous or metachronous LS-related cancer
Importance of Genetic Testing
Genetic testing is crucial in identifying hereditary syndromes, which impacts surveillance recommendations, surgical decisions, treatment options, and allows for cascade testing of family members who may benefit from enhanced screening and preventive measures 1. The most common hereditary syndromes tested for include Lynch syndrome and Familial Adenomatous Polyposis (FAP) 1.
Testing Approach
Testing typically involves tumor analysis first (microsatellite instability and immunohistochemistry), followed by germline genetic testing if abnormalities are found 1.
Benefits of Genetic Testing
The EGAPP Working Group concluded that there is moderate certainty that genetic testing for Lynch syndrome in patients with newly diagnosed colorectal cancer would provide moderate population benefit in reducing morbidity and mortality from Lynch syndrome in relatives 1.
From the Research
Genetic Testing for Colorectal Cancer
Genetic testing is advised in colorectal cancer when there is a family history of the disease or a personal history of colorectal cancer at a young age. The following are some scenarios where genetic testing is recommended:
- A family history of colorectal cancer, particularly if there are multiple cases of colorectal cancer in the family or if the cancer occurred at a young age 2, 3
- A personal history of colorectal cancer, especially if it occurred at a young age or if there are other signs of a hereditary cancer syndrome 3, 4
- A known family history of a hereditary cancer syndrome, such as Lynch syndrome or familial adenomatous polyposis (FAP) 5, 6
Indications for Genetic Testing
Genetic testing is indicated in the following situations:
- To confirm a diagnosis of a hereditary cancer syndrome, such as Lynch syndrome or FAP 5, 4
- To identify individuals who are at increased risk of developing colorectal cancer due to a family history of the disease 2, 3
- To guide cancer screening and prevention strategies, such as more frequent colonoscopies or prophylactic surgery 4
Types of Genetic Tests
There are several types of genetic tests that can be used to diagnose hereditary colorectal cancer syndromes, including: