As a genetic counselor specializing in cancer genetics, I’m happy to be contributing to the Ambry patient blog during National Colorectal Cancer Awareness Month. Colorectal cancer can happen by chance, but it can also be inherited. Your doctor or genetic counselor can evaluate your family history to determine if you should consider genetic testing for inherited forms of colorectal cancer. 

The most common cause of inherited colorectal cancer is Lynch syndrome (previously called HNPCC or hereditary non-polyposis colorectal cancer). Georgia Hurst, patient advocate with a family history of Lynch syndrome, discussed details about the condition in her blog post; you can also read more on the patient website here. People with Lynch syndrome can develop colorectal and other cancers at an earlier age than usual, so screening for these cancers earlier is important.

5 genes are currently associated with Lynch syndrome: MLH1, MSH2, MSH6, PMS2, and EPCAM. If your doctor or genetic counselor thinks that you could have Lynch syndrome, you may be offered testing for one or all of these genes. If you are found to have a mutation (misspelling) in one of these genes, this confirms you to be at increased risk for developing colorectal cancer. If you test positive for a Lynch syndrome gene mutation, your doctor will recommend starting your colonoscopies earlier, usually starting between ages 25-35. Your doctor can also discuss with you the best time period between colonoscopies, to remove any polyps that might form. 

It is important to remember that if you test positive for a Lynch syndrome gene mutation, it does not mean that you will get cancer, only that you have an increased risk of developing it. With regular colonoscopies, colon polyps can be removed to help prevent colorectal cancer. For women with Lynch syndrome your doctor may recommend screening for uterine (endometrial) cancer and ovarian cancer.  Following up with any screening is important to reduce your overall risk of developing cancer. 

And now, a very important point. Every family with Lynch syndrome is different, and each is considered individually beyond their genetic test result. The risk for developing colorectal cancer varies from gene to gene. Depending on the gene that is found to cause Lynch syndrome, some families may have a higher risk of developing colorectal cancer than other families. Some families with Lynch syndrome can additionally be at an increased risk to develop stomach cancer. In these families, doctors will often recommend doing a screening test called an upper endoscopy to screen for stomach cancer. This test can often be done at the same time as the colonoscopy. 

Let’s discuss an example: A man may test positive for a mutation in the MLH1 gene and have a family history of stomach cancer or kidney cancer. As such, his family members would be recommended to have screening for stomach and kidney cancers. However, screening for these cancers might not be recommended for someone that tests positive for a mutation in the PMS2 gene, but has no family history of stomach or kidney cancers.