Most cancers are caused by environmental, lifestyle or other factors, but as many as 10% of cancers are due to a hereditary condition. Lynch syndrome is the most common form of hereditary colon cancer and is responsible for 3-5% of colon/rectal cancers.
Lynch syndrome is caused by a mutation in one of the Mismatch Repair (MMR) genes. These genes check each copy of DNA for errors and, if a mismatch is found, repair it. These genes are inherited from your parents. If you inherit an MMR gene with a mutation, it cannot check DNA for these errors. However, the copy from your other parent can do the job. If at some point that second copy gets damaged, the cell cannot repair DNA and cancer develops.
Lynch syndrome patients are at higher risk of many cancer types: colon, rectal, uterine, ovarian, urinary tract, stomach, small intestine, pancreas and brain. The risk of colon cancer in Lynch syndrome is as high as 80%, and up to 50% for uterine cancer. There are specific guidelines which include both screening procedures, such as frequent endoscopies, and prophylactic surgery that can significantly lower the risk of cancer in patients with Lynch syndrome. Once we diagnose the syndrome, we can often prevent cancer in these individuals.
We are able to screen for Lynch syndrome by analyzing colon cancer cells that are removed at the time of surgery. Many of the hospitals in the area are doing this routinely, and will notify your surgeon if there is cause for concern. Further testing done from a blood sample can verify results, or reveal other genetic abnormalities that may cause hereditary colon cancer. We also do blood testing for genetic evaluation of those who have a family history of colon cancer.
Lynch syndrome is a “dominant” genetic disease. If you have Lynch syndrome, there is a 50% chance that your children could inherit it.
By taking a detailed personal and family history, your doctor will help determine if you should be evaluated for a Lynch syndrome. You should meet with a genetic specialist if you or a family member were diagnosed with colon or uterine cancer before the age of 50, or several members of your family have been diagnosed with colon, uterus or ovarian cancer.
Many people are concerned about genetic discrimination, such as being treated differently by employers or insurance agencies because of genetic results. Federal law prohibits this. The Genetic Information Nondiscrimination Act (GINA) is a federal law protecting people from genetic discrimination based on genetic testing results or family history. In addition, most insurers will cover genetic testing.
At Virginia Cancer Specialists, we have highly trained genetics team that includes two physicians, a genetic counselor and a nurse practitioner. If you have any questions about your personal or family history, we would be delighted to meet with you to determine if genetic testing is recommended, order the appropriate testing and discuss the implications of the results.
Patricia Rodriguez, M.D.