Li-Fraumeni Syndrome Health Article

Definition

Li-Fraumeni syndrome (LFS) is a genetic disorder caused by a hereditary mutation in a cancer susceptibility gene. Individuals with LFS have an increased risk for developing certain types of cancer, often at younger ages than is typically observed in the general population.

Description

Li-Fraumeni syndrome (LFS) was first described by Dr. Frederick Li and Dr. Joseph Fraumeni in 1969. It is caused by mutations in the TP53 gene, located on chromosome 17. The types of mutations that cause LFS are known as hereditary mutations, and therefore can be inherited, or passed from a parent to a child.

Cancer Risks

The TP53 gene is a tumor suppressor gene. When an individual inherits a mutation in this type of gene from one of their parents, they have an increased risk for developing certain kinds of cancer. The most common kinds of cancer associated with LFS are sarcomas, or tumors that arise in connective tissue, like bone or cartilage.

Females with LFS have an increased risk for developing breast cancer. Males and females may also be at risk for developing leukemia, melanoma, colon, pancreatic, and brain cancer. They may also develop adrenal-corticoid tumors, which develop on the outer surface of the adrenal glands. These cancers often occur at younger ages than are typically observed in the general population, often before age 45.

Some individuals with LFS may develop certain cancers, such as brain tumors, sarcomas, or adrenalcorticoid tumors in childhood. In addition, individuals with a mutation

in the TP53 gene have a higher risk for developing multiple primary cancers. For example, a person with LFS who develops a sarcoma at a young age and survives that cancer has an increased risk for developing a second, or possibly even a third different kind of cancer.

Genetic Counseling and Testing

Genetic testing for mutations in the TP53 gene is usually performed on a blood sample from the relative in the family who has had one of the cancers associated with LFS at a young age. One of the most effective ways to test for mutations in the TP53 gene is by sequencing, a process whereby the chemical components of a patient's DNA is compared to that of DNA that is known to be normal. If the entire DNA code of the TP53 gene is sequenced, it is believed that the majority (98%) of the (mutations) that are responsible for Li-Fraumeni syndrome can be identified. However, as the process of sequencing is a difficult and often time-consuming process, it is not always performed for every patient. Often, only specific areas of the TP53 gene, where there is most likely to be a mutation associated with LFS, are analyzed. The length of time to receive results depends on the extent of testing that is performed and the laboratory that is used.

Due to the fact that some of the cancers associated with LFS can occur at very young ages, there is a question as to whether or not genetic testing should be an option for at-risk children. Typically, genetic testing is not offered to anyone under the age of 18. However, because there are some screening options available for children with LFS, it is thought that the option of testing could not be denied if a parent feels that it is important for their son or daughter's future health. Groups such as the National Society of Genetic Counselors are beginning to explore the issue of genetic testing in minors (those under age 18) for mutations in cancer susceptibility gene, especially if these minors would be at risk for developing childhood cancers.

It is important to understand the various categories of results that are associated with undergoing genetic testing for mutations in the TP53 gene. A positive result indicates the presence of a genetic mutation that is known to be associated with an increased risk for developing the types of cancer associated with LFS. Once this kind of mutation has been found in an individual, it is possible to test this person's relatives, like their children, for the presence or absence of that particular mutation. Individuals who have a mutation in the TP53 gene have a 50% chance of passing on this mutation to their children.

Even if a patient has a mutation in the TP53 gene, it does not mean that they will definitely develop one of the cancers that are associated with Li-Fraumeni. However, the risk for those with the mutation is much higher than for someone in the general population. The likelihood that a person will develop cancer if they have a mutation in a cancer susceptibility gene like TP53 is called penetrance.

If the first person tested within a family is not found to have an alteration in the TP53 gene, their result is negative. Often this result is called indeterminate, because a negative test result cannot completely rule out the possibility of hereditary cancer being present within a family. The interpretation of this type of result can be very complex. For example, a negative result may mean that the method used to detect mutations in the TP53 gene may not be sensitive enough to identify all mutations. Additionally, the mutation might be located in a part of the gene that is difficult to analyze. It may also mean that a person has a mutation in another cancer susceptibility gene that has not yet been discovered or is very rare. Finally, a negative result could mean that the person tested does not have an increased risk for developing cancer because of a mutation in a single cancer susceptibility gene.