What is Lynch Syndrome ((HNPCC)?

Good Medical Care and Early Cancer Screening Can Manage Lynch Syndrome Risks

What is Lynch syndrome or hereditary nonpolyposis colorectal cancer?. Credit: Istockphoto.com/Stock Photo©Svisio

Lynch syndrome or 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 (HNPCC), Genetics, and Familial Colon Cancers

About 75% of colon cancers are sporadic cases. This means they have no known genetic cause or documented family history for the individual who is diagnosed with the disease.

Among the other causes of colon cancer is Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC).

Lynch syndrome accounts for 2-7% of colorectal cancer cases diagnosed in the US. Given that about 160,000 people are diagnosed with colon cancer each year, this means between 3,200 and 11,200 of those colon cancer cases are attributable to Lynch syndrome.

Along with an increased risk of colon cancer, people with Lynch syndrome can 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.

This is also the reason it's important to write out your family history.

  People often don't think of some cancers as hereditary, but when added together the link appears.

How is Lynch Syndrome 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, when they pass along their genes.

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 genetic links to colon cancer that are important to understand 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, and even if someone has a genetic risk, we are learning more about other 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% has a genetic link.  The 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 a 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 doctor about getting a referral to see a genetic counselor. Your doctor 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. Seeing a genetic counselor is important because not all changes to affected genes result in the same level of cancer risk. Some changes may increase risk only slightly, while other changes can greatly increase cancer risk. It is important to know your own personal risk so you can develop a plan to manage it.

Cancer Screening

The second important step you can take is to talk to your doctor 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.

As the name hereditary nonpolyposis colorectal cancer suggests, this condition increases colon cancer risk without always increasing the risk of polyps. Polyps are growths in the colon that if untreated, can develop into colon cancer. This does not mean that people with Lynch syndrome don't ever get polyps. It simply indicates that they more often develop colon cancer without first developing polyps. For this reason, colonoscopy screening for this disease can be more challenging, but research supports that colonoscopy really does detect the colon cancers associated with Lynch syndrome. Colonoscopy is an important part of managing Lynch syndrome.

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 a very serious inconvenience, it is one of the best ways to manage your increased risk of cancer, including colon cancer.

There is Some Good News

While nobody wants to have Lynch syndrome, there is one bit of good news regarding this genetic condition. In 2008, Italian researchers published research showing that colorectal cancer patients with Lynch syndrome do much better than other colon cancer patients. People with Lynch syndrome have significantly better survival, with 94% of these patients still alive five years after diagnosis, compared to a 5-year survival rate of 75% for those with sporadic colon cancer. There are several possible reasons for this, ranging from earlier detection in people with Lynch syndrome because they are better about getting colon cancer screening to differences in the biology of the different types of colon cancer. Either way, this is reassuring news.

Sources

Colorectal Cancer Coalition. Lynch Syndrome. Accessed: 02/21/16.http://fightcolorectalcancer.org/prevent-it/risk-factors/lynch-syndrome

Gene Reviews. Hereditary Non-Polyposis Colon Cancer. Accessed 02/21/16. http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=hnpcc

Genetic and Rare Diseases Information Center. Accessed: 02/21/16. http://rarediseases.info.nih.gov/GARD/

Lindor NM. Making a case for surveillance colonoscopy in Lynch syndrome. Colorectal Disease,  2009 11:131-32.

The National Institutes of Health. Lynch Syndrome. Accessed: 02/21/16. http://ghr.nlm.nih.gov/condition=lynchsyndrome

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