Lynch Syndrome

By Peter Galvin, MD

Lynch syndrome, known as hereditary nonpolyposis colorectal cancer, is the most common cause of inherited colorectal cancer and affects approximately 1.2 million individuals in the U.S. It is a genetic disease in which people have a 50% chance of inheriting specific gene variants involved in repairing damaged DNA if one of their parents has Lynch syndrome. The lifetime risk of cancer, which can be between 10% to 80%, depends on which gene is affected and may be increased by lifestyle choices such as smoking and alcohol use. Lynch syndrome is associated with not just colorectal cancer, but also cancers of the uterus, ovary, stomach, pancreas, kidney, bladder and ureters (the tubes between the kidneys and bladder), prostate, small bowel, biliary tract, brain, and skin (especially squamous cell). These cancers are often diagnosed before age 50 years.

It is diagnosed by a blood test and genetic analysis. Of course, not everyone should get tested for Lynch syndrome. There are Amsterdam and Bethesda criteria for determining who might benefit from genetic testing. The Amsterdam criteria assess the risk of Lynch syndrome based on family history. People who have at least three relatives diagnosed with a type of cancer associated with Lynch syndrome and who meet all of the following criteria are at risk of Lynch syndrome: (1) one relative is a first-degree relative (parent, sibling, or child) of the 2 other relatives; (2) at least two successive generations are affected; and (3) at least one relative had cancer diagnosed before age 50 years.

The Bethesda criteria assess the risk for people diagnosed with colorectal cancer. Individuals are at risk if they: (1) had been diagnosed with colorectal or uterine cancer before age 50 years; (2) have been diagnosed with a second cancer or another cancer associated with Lynch syndrome (see above); (3) are younger than 60 years and have a cancer characteristic of Lynch syndrome when viewed under a microscope; (4) have a first-degree relative younger than 50 years who was diagnosed with colorectal cancer or another cancer associated with Lynch syndrome; and (5) have two or more first- or second degree relatives (aunt, uncle, niece, nephew, or grandparent) with colorectal cancer or a Lynch syndrome-associated cancer at any age.

Individuals with Lynch syndrome should undergo colonoscopy to screen for colorectal cancer and pre-cancerous polyps starting at age 20 to 25 years or at an age that is 2 to 5 years younger than the earliest colorectal cancer diagnosis in the family, whichever is earlier. Following that, colonoscopy should be performed every one to two years. Some people may undergo screening for other cancers associated with Lynch syndrome if they have a family history of these cancers. Finally, there is no cure for Lynch syndrome as the human genetic code is unchangeable, at present anyway. For more information go to the website of the American Cancer Society at www.cancer.org

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