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 herditary 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
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 onto 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 disease 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.
Your Best Defense
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.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 can 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 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. Last year, 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
Colon Cancer Alliance. Genetics of Colon Cancer. Accessed: Mar 16, 2009.
http://www.ccalliance.org/what_diseaseinfo_genetics.html
Colorectal Cancer Coalition. Lynch Syndrome. Accessed: Mar 16, 2009.
http://fightcolorectalcancer.org/tag/lynch_syndrome
Gene Reviews. Hereditary Non-Polyposis Colon Cancer. Accessed Mar 16, 2009.
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=hnpcc
Genetic and Rare Diseases Information Center. Accessed: Mar 16, 2009.
http://rarediseases.info.nih.gov/GARD/
Lindor NM. Making a case for surveillance colonoscopy in Lynch syndrome. Colorectal Dis 2009 11:131-32.
National Society of Genetic Counselors. Accessed: Mar 16, 2009.
http://www.nsgc.org/.
The National Institutes of Health. Lynch Syndrome. Accessed: Mar 16, 2009.
http://ghr.nlm.nih.gov/condition=lynchsyndrome
