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Sunday, November 29, 2015
Lynch Syndrome and Brain Cancer
How common is Brain Cancer for someone with Lynch Syndrome? I have had colon cancer (age 23) and renal cell (age 45). Genetic testing was positive for MLh1 mutation.
You ask a challenging question; in trying to find an answer to your question, there were only 3-4 studies that clearly reported on this information. It appears that the lifetime risk to develop brain cancer in Lynch syndrome, or HNPCC (hereditary non-polyposis colorectal cancer susceptibilty) is on the order of 2-5%. This may be an over-estimation, as a number of studies did not report finding brain cancers in their study populations. For more detailed information, you should contact the genetic counselor you worked with when you had testing; if you did not work with a genetic counselor, it would be a good idea to find a genetic counselor near where you live. I have attached a website for the National Societ of Genetic Counselors. This should help you find a genetic counselor.
As background information, Lynch syndrome, or HNPCC, is one of the colon cancer susceptibility syndromes. It is caused by mutations in a class of genes called the "mismatch repair genes." The three mismatch repair genes that account for most of the families with HNPCC are called "MLH1", "MSH2" and MSH6." There are at least three other genes that are included in this class of genes, but they appear to be responsible for only a small proportion of hereditary colon cancer.
Having a mutation in one of these genes increases one's chance of developing a number of cancers, but predominantly colon cancer, uterine or endometrial cancer, ovarian cancer, gastric cancer, and cancers of the genitouriary tract. The exact cancer risk varies between genes. Individuals who are found to have HNPCC, or those who have family members with HNPCC should begin colon cancer screening in their early 20s, and they should have colonoscopies every 1-2 years. Women with HNPCC should also have regular screening for uterine cancer and ovarian cancer beginning in their 30s, or should consider having their ovaries and uterus removed once they finish having children.
As with most hereditary cancer syndromes, HNPCC is inherited in an autosomal dominant manner; this means that each child of an individual with HNPCC will have 50% chance of inheriting the susceptibilty from their parent, and will have a substantially increased risk for colon and other cancers. They will need to begin cancer screening substantially earlier than the average man or woman will. If a child does not inherit the HNPCC mutation, they will not be at substantially increased risk to develop cancer. They will still have the same cancer risk as the average man or woman.
For additional information about HNPCC you can visit the website for National Cancer Institutes. The website is listed below.
Duane D Culler, PhD, MS
Clinical Instructor of Genetics
School of Medicine
Case Western Reserve University