Understanding Lynch syndrome: The genetic link to colorectal cancer

Pim Suwannarat, M.D., is a board-certified geneticist and chief of Genetics at the Mid-Atlantic Permanente Medical Group. She sees patients at the Kaiser Permanente Marlow Heights Medical Center.

You may know that lifestyle factors such as smoking, drinking alcohol in excess and eating a diet high in red meat increase your risk of colorectal cancer.

But did you know there is an inherited genetic disorder linked to an increased risk of colorectal cancer? Lynch syndrome (also called hereditary non-polyposis colorectal cancer) is the most common inherited colorectal cancer syndrome*, with an estimated 1 in 300 people having the disorder.

A diagnosis of Lynch syndrome influences Dickdarmkrebs prevention and screening. As a board-certified geneticist, my job is to make people aware of Lynch syndrome and what it means for colorectal cancer screening. Here’s what I want you to know when it comes to this risk factor—and what you can do to stay on top of your health:

What is Lynch syndrome?

Lynch syndrome is a genetic syndrome associated with an increased risk of colorectal cancer as well as ovarian cancer, uterine cancer and other cancers of the gastrointestinal tract, including stomach and pancreatic cancers.

If I have Lynch syndrome, will I get cancer?

Not necessarily! People with Lynch syndrome do not always get cancer.  Lynch syndrome is usually caused by a mutation of one of five genes: MLH1, MSH2, MSH6, PMS2 oder EPCAM. Depending on which gene is affected, a patient with Lynch syndrome’s lifetime risk of developing colorectal cancer is 9%-61%, compared with about 4% for those who do not have Lynch syndrome.¹

The numbers may sound scary, but awareness of Lynch syndrome enables people to take charge of their health.

How do I know if I have Lynch syndrome?

People with Lynch syndrome do not have any symptoms unless or until they develop cancer. The only way to know for sure is to undergo genetic testing or tumor screening followed by genetic testing. You should consider genetic testing if:

• You have had a colorectal cancer diagnosis. The tumor can be tested for indicators of Lynch syndrome and based on this, additional genetic testing may be recommended to check your risk for other types of cancer. You can also inform family members, who may opt to get tested.
• You have a first-degree family member who has Lynch syndrome.
• You have multiple close relatives who have had cancers associated with Lynch syndrome (colorectal cancer, other gastrointestinal tract cancers, uterine cancer, endometrial cancer and more), particularly if they were diagnosed at a young age (under age 50).

Check with your insurance company before meeting with a genetic counselor or health care provider to see if the meeting and/or genetic testing are covered by your insurance. If testing is not covered, explore free and low-cost options available near you.

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Although most people who have cancer do not have a genetic mutation—only 5%-10% of cancer cases are caused by hereditary gene mutations—it’s a good idea to discuss your family health history and learn whether you could be at higher risk for cancer. Use this tool to gather your family health history and discuss it with your health care provider.

If I find out I have Lynch syndrome, I think I will be really scared. What should I do?

Knowing about a genetic condition may take an emotional toll. Some people may choose not to find out whether they have Lynch syndrome, and that’s okay. But as a geneticist, I often remind people that knowledge is power—if you are tested and do find out you have Lynch syndrome, you can take steps proactively to lower your risk of developing colorectal and other cancers. You’ll also have more information about the types of screenings you need, the warning signs to be aware of, and the importance of staying on top of your health care appointments.

Regardless of your decision, everyone should get Routinemäßige Krebsvorsorgeuntersuchungen to prevent cancer or detect it early, when successful treatment is more likely.  Even if you test negative for these mutations, you would still carry the same risk as the general population and would need to follow screening recommendations for those at average risk—you can check with your health care provider to learn more about what’s right for you.

Colorectal cancer screening is recommended for people at average risk starting at age 45, with a colonoscopy, an at-home, stool-based test or another type of test. If you have Lynch syndrome, you will be advised to start screening with a colonoscopy at a younger age, sometimes as early as your 20s. While colonoscopies are usually recommended every 10 years, people with Lynch syndrome may need to repeat them every couple of years.

Colonoscopies are typically the recommended screening method for those at increased risk due to the ability to find and remove precancerous polyps during the procedure before they potentially turn into cancer.

Is there a cure for Lynch syndrome?

While there’s no cure for Lynch syndrome, we know a lot about gene-specific risk for people with the syndrome. If you have Lynch syndrome, your health care team can work with you to develop a cancer screening plan that is tailored toward your specific mutation.

Early Detection = Better Outcomes, and many cancers are more treatable than ever before. If you are concerned about Lynch syndrome, reach out to your doctor to discuss whether genetic testing is right for you.

*While the most common inherited syndrome linked with colorectal cancers is Lynch syndrome, familial adenomatous polyposis (FAP) and other rarer syndromes exist and can increase the risk of colorectal cancer. Genetic testing could also include testing for these syndromes.

¹ Genetic/Familial High-Risk Assessment: Colorectal, Endometrial, and Gastric: Guidelines Detail [Internet]. National Comprehensive Cancer Network; 2024 [cited 2024 Oct 16]. Available from: https://www.nccn.org/guidelines/guidelines-detail?category=2&id=1544