Lynch Syndrome, Genetics, and Screenings

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J.J. Singleton learned he had Lynch syndrome—a hereditary condition linked to colorectal cancer—after he was diagnosed with colon cancer in 2015 at age 27. It came as a surprise: Singleton’s family has had very little cancer history. His grandmother had three brothers who died young, however, so his doctors speculate that there may have been a cancer risk that the family never discovered.

This diagnosis helped Singleton in two ways: One, it gave his doctors valuable information about his tumor that helped them match Singleton to the treatments best for him. And two, it helped his family learn more about their level of risk for colorectal and other cancers. Right away, Singleton encouraged his parents and siblings to get screened, too. They all tested negative.

“People may get scared when they hear about genetic mutations or Lynch syndrome because it’s something you deal with for life. But this is about your life–this isn’t a death sentence."

- J.J. Singleton, 2022 Ambassador and stage IV survivor

What Lynch Syndrome Is

Colorectal cancer isn’t usually hereditary. Only about 5% to 10% of people with colorectal cancer have it due to a hereditary cause. Of those, however, the most common cause is Lynch syndrome. Not everyone who has Lynch syndrome will get cancer, but everyone with Lynch syndrome carries a higher risk for certain cancers, including colorectal, endometrial, ovarian, urinary system, and gastrointestinal cancers.

The condition results from a mutation in one of five genes, and each of those genes carries a different risk level for these cancers. For example, if there’s a mutation in the MLH1 gene, then the risk of colorectal cancer is about 50%; if the mutation is in the PRMS2 gene, then it’s between 8% to 20% risk. Although a Lynch syndrome diagnosis can be difficult to receive, it comes with important information that helps the person diagnosed take proactive steps to protect their health.

How Lynch Syndrome Affects Cancer Screening Recommendations

When someone tests positive for Lynch syndrome, they learn more about their level of risk for certain cancers, which then informs how often they should get screened for those cancers.

“While hereditary cancer syndromes like Lynch syndrome account for a very small portion of cancer diagnoses, it's important to identify if they are occurring,” says Dr. Jennifer Weiss, Director of Gastrointestinal Genetics Clinic at UW. “The screening recommendations for individuals with one of these high-risk syndromes are very different than what we recommend for the general population. So it's important to identify this if we think this is happening in a family.”

If someone tests positive for Lynch syndrome, they should do what Singleton did: Encourage their close relatives to get tested, too. It can help an entire family take informed, proactive steps in cancer prevention.

“For example, it takes—in general—about 10 to 15 years for normal colon tissue to become a precancerous polyp and then to a slightly larger polyp before turning into a cancer,” Dr. Weiss says. “So we have time to intervene, to find these polyps during a colonoscopy, and take them out before they turn into cancer.”

A Lynch Syndrome Diagnosis Can Improve Cancer Treatments

A Lynch syndrome diagnosis can also help people who already have cancer by giving their care teams additional information about their tumor. Colorectal cancer caused by Lynch syndrome can behave somewhat differently than cancers that don’t have a hereditary cause. It may affect different parts of an organ or grow at a faster rate. When an oncologist learns more about a tumor, they can find more effective treatments for it.

“Learning about the mutations in my tumor caused by Lynch syndrome pretty much set me on the path of which treatments my doctors wanted me to try first,” Singleton says.

Should You Get Screened for Lynch Syndrome?

If you have or have had colorectal cancer—or if you have several family members who have cancers associated with Lynch syndrome or who have Lynch syndrome—you should get tested for Lynch syndrome. Dr. Weiss encourages people to visit their primary care provider to learn about their level of risk and, if needed, to get a referral to a genetic counselor. Even if there are no genetic counselors in the area, Dr. Weiss says that telehealth providers can mail genetic tests to you. You can complete the test at home and mail it back with the shipping package that’s included with the testing kit. People with increased risk can usually get the cost of these screening tests covered by insurance.

Singleton says that he understands people’s discomfort with getting tested; he says that he used to feel that way too. But he’s discovered that more information will only help you, your doctor, and even those around you.

“I totally understand [the unease], but I try to explain to people that getting tested is one day of being uncomfortable. I don’t want to see anyone sitting in a chemo chair beside me,” he says.

Dr. Weiss also encourages families to be open and to share information with their families, so that everyone can understand their level of risk and take the steps needed to prevent cancer.

“Most people aren’t sitting around their table during the Holidays telling people what kind of polyps they had removed during their colonoscopy,” Dr. Weiss says. “But this is important information to share with each other.”

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Learn more about Lynch syndrome and other hereditary causes of colorectal cancer.