Li-Fraumeni syndrome

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 adrenalcorticoid 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.

Screening and Prevention Options

With the exception of screening for breast cancer, there are no effective means to screen for and/or prevent the cancers that are associated with Li-Fraumeni syndrome. However, researchers have developed some screening guidelines for those with LFS. For men and women, it is recommended that they undergo a thorough physical exam with their doctor every year. This should include skin and colon cancer screening along with a complete exam of the nervous system. Women should also undergo breast cancer screening, which consists of annual mammograms, self-breast exams, and breast exams by a physician or health care provider. Individuals with Li-Fraumeni syndrome may choose to undergo screening more often and at an earlier age then people in the general population.

For children with a TP53 mutation, it is recommended that they also undergo a complete physical exam once a year by their physician. This should include an analysis of their urine and blood and an abdominal ultrasound.

Age of onsetType of cancerInfancyDevelopment of adrenocortical carcinomaUnder five years of ageDevelopment of soft-tissue sarcomasChildhood and young adulthoodAcute leukemias and brain tumorsAdolescenceOsteosarcomasTwenties to thirtiesPremenopausal breast cancer is common

KEY TERMS

Adrenalcorticoid tumors

Cancer that arises on the outer surface of the adrenal glands.

Adrenal glands

Structures located on top of the kidneys that secrete hormones.

Cancer

The process by which cells grow out of control and subsequently invade nearby cells and tissue.

Cancer susceptibility gene

The type of genes involved in cancer. If a mutation is identified in this type of gene it does not reveal whether or not a person has cancer, but rather whether an individual has an increased risk (is susceptible) to develop cancer (or develop cancer again) in the future.

Chromosome

Structures found in the center of a human cell on which genes are located.

Gene

Packages of DNA that control the growth, development and normal function of the body.

Genetic counselor

A specially trained health care provider who helps individuals understand if a disease (such as cancer) is running in their family and their risk for inheriting this disease. Genetic counselors also discuss the benefits, risks and limitations of genetic testing with patients.

Leukemia

Cancer that arises in blood cells.

Mutation

An alteration in the number or order of the DNA sequence of a gene.

Mammogram

A screening test that uses x rays to look at a woman's breasts for any abnormalities, such as cancer.

Penetrance

The likelihood that a person will develop a disease (such as cancer), if they have a mutation in a gene that increases their risk for developing that disorder.

Sarcoma

Cancer that occurs in connective tissue, such as cartilage or bone.

Sequencing

A method of performing genetic testing where the chemical order of a patient's DNA is compared to that of normal DNA.

Tumor suppressor gene

Genes that typically prevent cells from growing out of control and forming tumors that may be cancerous.

Ultrasound

A test that uses sound waves to examine organs in the body

QUESTIONS TO ASK THE DOCTOR
• What is the likelihood that the cancer in my family is due to a mutation in a cancer susceptibility gene, particularly the TP53 gene?

• If my family is found to have Li-Fraumeni syndrome, what is the chance that I carry a mutation in the TP53 gene?

• What are the benefits, limitations and risks of undergoing genetic testing?

• What is the cost of genetic testing and how long will it take to obtain results?

• If I undergo genetic testing, will my insurance company pay for testing? If so, will I want to share my results with them?

• What does a positive test result mean for me?

• What does a negative test result mean for me?

• If I test positive for a mutation in a cancer susceptibility gene, what are the best options available for screening and prevention? What research studies may I be eligible to participate in?

• What legislation is in effect to protect me against discrimination by my insurer or employer?