A person's family history of cancer can be a good indicator of whether they should be screened for a hereditary colon cancer condition, such as Lynch syndrome. Factors of family history include:
- Types of cancer: colorectal, endometrial, small intestine, ureter, or renal pelvis cancer
- Number of relatives and generations affected with cancer: three or more relatives across two or more generations
- Age of onset of cancer: diagnosis before age 50
The greatest risk for having Lynch syndrome is having a relative with this condition. The first-degree relatives of an individual with Lynch syndrome have a 50 percent chance of having the same mutation, and should be counseled for genetic testing.
People with a family history of colorectal cancer diagnosed at an early age may also want to be screened for familial adenomatous polyposis, or FAP. FAP is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition. Mutation can be spontaneous during embryo development, however, and thus would not have a significant family history.
Genetic or germline testing can be done using a blood or saliva sample to screen for the gene mutations that cause Lynch syndrome and familial adenomatous polyposis.
Because there is no cure for genetic conditions, surveillance for eventual cancer development is important for affected individuals. People with Lynch syndrome or FAP should be screened for colorectal cancer starting at age 20 to 25, and every one to two years thereafter. People with Lynch syndrome should also be screened for other cancers starting at age 30 to 35, and a woman may need to have her uterus and ovaries removed to prevent cancer completely.