It has been estimated that about 5-10% of all colon and endometrial cancer cases run in families; in other words, they are hereditary and occur as a result of an inherited predisposition. Of the cases of colon and endometrial cancer that are hereditary, approximately half are due to Lynch syndrome. There are additional known and unknown genes that account for the remaining cases of hereditary colon and endometrial cancer.
Features of cancers with a strong inherited component include families with early onset colon or endometrial cancer (before age 50), multiple primary cancers in an individual, and multiple generations affected with colon and endometrial cancer. Also, individuals with Lynch Syndrome are at increased risk to develop other gastrointestinal cancers (ie stomach and pancreatic cancer), ovarian and urinary tract cancers.
A person inherits an increased risk to develop colon and endometrial cancer if they inherit a mutation in one of several genes associated with Lynch syndrome. These genes are called MLH1, MSH2, MSH6, PMS2, and EPCAM. When these genes are working properly, their job is to suppress tumor growth and to protect us from cancer. An inherited mutation in these genes may be the first step in an accumulation of errors in many other genes that can lead to a cell becoming cancerous. This is also why individuals with one Lynch syndrome gene mutation may be diagnosed with colon or endometrial cancer before the age of 50, and may develop multiple cancer primaries.
All individuals have two copies of each gene, one copy from each parent. If an individual carries a Lynch syndrome mutation, it was most likely inherited from one of his parents. There is a 50% chance that siblings and children of a person who carries a mutation will have inherited it as well.
Individuals who inherit an MLH1, MSH2, MSH6, PMS2, OR EPCAM mutation have an increased risk for developing colon cancer and endometrial cancer (for women). Additionally, there are slightly increased risks for other types of cancer, including upper GI, pancreatic, ovarian and urinary tract cancers. These risks may vary from family to family and from one individual to another. People who have an altered Lynch syndrome gene have a 55 – 85% chance of developing colon cancer by age 70. Their risk for women to develop endometrial cancer ranges from 30 – 60% by age 70. A person who has already had colon cancer has an increased risk to develop a second colon cancer.
The implications of negative results will vary depending on the personal and family history of the individual being tested. Results are more meaningful if someone else if the family has tested positively. It is important to report any genetic testing results of your family members to the genetic counselor to help clarify your own result.
A person with Lynch syndrome has several choices that should be discussed with their physician. Enhanced screening methods can help find cancers at the earliest possible stage when they are most easily treated. Regular colonoscopy, transvaginal ultrasound, ovarian cancer screening, and upper GI evaluation should be discussed with your physician.
Another option is to have surgery to remove at-risk tissue before cancer develops. An example of this would be a total removal of the uterus and ovaries to reduce the risk of endometrial and ovarian cancer, or a sub-total colectomy to reduce the risk of colon cancer. It is important to note that while surgery provides the greatest form of cancer risk reduction, no surgery can completely eliminate one’s chances of getting cancer in the future.
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The decision to have genetic testing for cancer risk is a complicated one. Individuals and families must not only weigh the risks and benefits of testing, they must also consider their unique situations. The process of genetic testing may be emotionally difficult regardless of whether a mutation is found.
Currently, it is against the law for medical insurance companies or employers to discriminate based on genetic testing. Genetic information may be considered by other insurance policies, like disability, long term care or life insurance.
The possible advantages of learning Lynch syndrome genetic test results include reduced uncertainty about cancer risks. This reduced uncertainty can relieve anxiety and can help individuals make informed decisions about their health care.