Preventing Colon Cancer With Hereditary Lynch Syndrome

Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), increases the risk of developing colon and other cancers. Medical care and a comprehensive cancer screening program can manage these risks.

Lynch Syndrome, Genetics, and Familial Colon Cancers

About 75% of colon cancers are sporadic cases, meaning there is no hereditary cause or family history of the disease. The remaining 25% occur in individuals who have some form of family history or genetic cause, including Lynch syndrome.

Among the nearly 150,000 people diagnosed with colorectal cancers each year, Lynch syndrome is associated with about 4,000 cases. People with Lynch syndrome can also have an increased risk of developing other cancers, including cancers of the rectum, stomach, small intestine, liver, gallbladder ducts, upper urinary tract, brain, skin, prostate, uterus (endometrium), and ovaries.

Families in which Lynch syndrome is present typically have a strong family history of cancer. With genetic testing becoming more widely available, many of these families are aware that they have the genetic changes that cause Lynch syndrome.

It is important to understand and speak with your healthcare provider about your family medical history in order to help determine what, if any, preventive tests might be appropriate to check for colon and other cancers.

How Lynch Syndrome Is Inherited

Lynch syndrome is passed from parents to children due to changes in four genes: MLH1, MSH2, MSH6, and PMS2. Genes are the instruction manual for building and running the human body.

Nearly every cell in our bodies contains two copies of each gene. One copy comes from your mother and one copy comes from your father. In this way, if a mother or a father has the changes in one or more of the genes that cause Lynch syndrome, they may pass these changes on to their children.

For some diseases, if one of the two gene copies is damaged or missing, the other "good" copy will function normally, and there will be no disease or increased risk of disease. This is called an autosomal recessive pattern.

For other diseases, including Lynch syndrome, if even one copy of a pair of genes is damaged or missing, this is enough to increase risk or cause disease. This is called an autosomal dominant pattern.

However, it is important to remember that only the higher risk of cancer is inherited in people with Lynch syndrome. Cancer itself is not inherited and not everyone who has Lynch syndrome will develop cancer.

In addition to Lynch syndrome, there are other known genetic links to colon cancer, and it's likely that even more connections will be discovered in the near future.

Your Best Defense

Thankfully we live in an era in which you don't have to just wait and see. There are ways of evaluating genetics to determine if a risk for disease exists and, if yes, what can be done to manage this risk.

Even if someone has a genetic risk, we are learning more about ways to lower that risk. Having a family history of cancer is not always a bad thing when it empowers people to take care of their health. 

An example of this is with breast cancer, for which around 10% have a genetic link. Women with a family history often make sure they are screened and don't wait to have a lump checked out. If they do develop cancer, it may consequently be found earlier than for someone in the 90% who is less concerned because of a lack of family history. 

Thinking about the predisposition in this way has helped some people better cope with their risk.

Genetic Counseling

If you find out that you have Lynch syndrome, talk to your healthcare provider about getting a referral to see a genetic counselor. Your practitioner can help you find a qualified genetic counselor in your area or you can search the National Society of Genetic Counselors website to locate genetic counseling resources.

Having a better understanding of the risk levels associated with your genes can help ensure any treatment or prevention plan is tailored to your case.

Cancer Screening

The second important step you can take is to talk to your healthcare provider about a cancer screening plan. For many cancer types, including colon cancer, easily accessible screening tests are available. And even for cancer types that don't have a designated screening test, tools such as CT scans and MRI tests may be used to find cancer at its earliest stages, when it's most curable.

Clinical Guidelines for Colon Cancer Screening

In Spring 2021, both the U.S. Preventive Services Task Force and the American College of Gastroenterology updated their respective clinical guidelines for colon cancer screening to start at age 45 instead of 50 due to increasing rates of colon cancer diagnoses under the age of 50. People with certain risk factors, including a family history of Lynch syndrome, may require earlier screening.

You will likely need to be screened starting at a younger age and more frequently than people without Lynch syndrome. While this may seem like an inconvenience, it is one of the best ways to manage your increased risk of cancer, including colon cancer.

6 Sources
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  3. U.S. National Library of Medicine. Lynch syndrome.

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  6. US Preventive Services Task Force, Davidson KW, Barry MJ, et al. Screening for colorectal cancer: US Preventive Services Task Force recommendation statement. JAMA. 2021 May 18;325(19):1965-1977. doi: 10.1001/jama.2021.6238.

By Suzanne Dixon, MPH, RD
Suzanne Dixon, MPH, MS, RDN, is an award-winning registered dietitian and epidemiologist, as well as an expert in cancer prevention and management.