Lynch Syndrome and the Genetics of Colon Cancer

Knowing your risk means you can do something about it
Lynch Syndrome and the Genetics of Colon Cancer

If you are 50 or older, you probably know you need regular screenings to prevent colon cancer. But did you know that some people need screenings much earlier in life?

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For people with Lynch syndrome, the most common genetic cause of colorectal cancer, the risk starts as early as age 25. Fortunately, knowing if you are at risk gives you a chance to do something about it.

How big is the risk?

Lynch syndrome accounts for about 3 to 5 percent of all colon cancers. In the Western world, a man with Lynch syndrome — also known as hereditary non-polyposis colorectal cancer (HNPCC) — has an 85 percent lifetime risk of colon cancer, compared with just 5 percent in the general population. Women with Lynch syndrome have a 40 percent lifetime risk of colon cancer, as well as a 40 percent risk of endometrial cancer — nearly 10 times the risk of most women.

I say “Western world” because in areas of the Far East such as Japan and China, people with Lynch syndrome also have a high risk of gastric cancer. It’s an example of how your genetic environment affects your risk for disease.

“Ask your surgeon if your hospital screens for Lynch syndrome. Knowing the results could literally save your life.”

Charis Eng, MD, PhD

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Founding Chairwoman of the Genomic Medicine Institute

How do we find it?

Sadly, a person’s first case of colon cancer is often how we diagnose Lynch syndrome. But once we make a diagnosis, we can work to make sure the first case is the only time they develop cancer with symptoms.

We search for mutations in three major genes: MLH1, MSH2 and MSH6. These genes are like copy editors; they search for and fix typographical errors in your DNA. If these genes are altered, the DNA errors start to add up. Fortunately, we can quickly spot these genetic alterations through microsatellite instability (MSI) testing and immunohistochemistry (IHC) testing of the colon cancer tissue. At Cleveland Clinic, we do one or both of these tests for every single case of colon cancer that is surgically removed at the Clinic. It’s automatic.

Further, in an eight-year study we recently published, we showed that referrals of positive screenings and outcomes are much better if these patients and tests are handled by a genetic counselor. A genetic counselor acts as a point person who keeps everyone — patient, surgeon, oncologist and other members of the medical team — in the loop. They also act as the translator of difficult genetics concepts for the patient and the family.

When we do this, we find cases of Lynch syndrome that might slip through the cracks otherwise.  

What does it mean for you?

Knowing your risk means knowing what steps you can take to avoid cancer:

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  • Monitoring: Men and women with Lynch syndrome need annual colon cancer screenings starting at age 25. Women in their 30s and 40s should have regular biopsies of the endometrium, then regular ultrasounds after menopause.
  • Prophylactic surgery: Your surgeon may recommend removing all of your colon if your risk of colon cancer is especially high. At-risk women also may consider removal of the uterus and ovaries to prevent other forms of cancer.
  • Family screening: Studies show that if we identify one person with Lynch syndrome, an average of two and a half family members also will have it. They probably won’t have any symptoms. Knowing if they have Lynch syndrome can help keep it that way.

If you have a family history of colon cancer or Lynch syndrome, ask to see a genetic counselor. If you are going through colon cancer and are having part of your colon removed, ask your surgeon if your hospital screens for Lynch syndrome. Knowing the results could literally save your life.

Related colon cancer resources

Web Chat on the Genetic Risk of Colon Cancer: Experts Answer Your Questions
March 27, 2013
10:30 a.m. (EST)

Sanford R. Weiss, MD Center for Hereditary Colorectal Neoplasia

Genomic Medicine Institute

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