In 1969, a remarkable cancer predisposition syndrome was reported by Li and Fraumeni. Li-Fraumeni syndrome (LFS) is an inherited autosomal dominant disorder that is usually associated with abnormalities in the tumor suppressor protein P53 gene (TP53) located on chromosome 17p13. It is also known as the sarcoma, breast, leukemia, and adrenal gland (SBLA) cancer syndrome. LFS variants include LFS1, LFS2, LFSL. LFS1 is associated with mutations in TP53, tumor suppressor gene. LFS2 is associated with mutations in CHEK2 (checkpoint kinase two), a tumor suppressor gene. LFS-L are individuals that do not have detectable mutations in P53.
There are three genes identified with Li-Fraumeni syndrome (LFS) Tp53 17p13, 1q23, and Checkpoint kinase two genes CHEK2 locus at 22q12.1. In these three genes, TP53 mutations are most common. P53 has many mechanisms of anticancer function; it plays a role in apoptosis, maintaining genomic stability, and inhibits angiogenesis. When DNA has sustained damage, it plays a role in the activation of DNA repair proteins. It can stop cell growth at the G1/S regulation point, which gives time for DNA repair proteins to fix the damage. If the damage is irreversible, it can trigger apoptosis. Checkpoint Kinase 2 (Chek2) regulates the activities of P53.
In TP53 mutations, one mutant allele is generally inherited by individuals with Li-Fraumeni syndrome; other allele is deleted or somatically mutated, which leads to loss of functional P53 protein. Missense mutations are the most common to occur, usually in exons 5 to 8 which is the DNA binding region of the gene. When mutation testing is done targeting exons 5-8 (these are the usual targets for testing), nearly 70% of Li–Fraumeni families meeting the required diagnostic criteria harbor P53 mutations. Partial loss of alleles present with less family history, decreased numbers of tumors, and late disease onset.
Not all individuals with Li-Fraumeni syndrome have TP53 mutations. It also can be due to an alteration in gene promoter which causes defective protein expression. It may also be due to new mutations that have not been described.
Li-Fraumeni (LFS) is a rare syndrome, 400 families with LFS have been reported in the literature. Children with a diagnosis of adrenocortical carcinoma have the highest occurrence of P53 mutations. The syndrome is also associated with childhood brain tumors, osteosarcomas, and rhabdomyosarcomas. Patients with multiple primary tumors have a high incidence of P53 mutations.
Mutations in the core binding protein of TP53 have an increased risk of cancer. TP53 mutations have a high penetrance. The lifetime risk for women is 90 percent by age 60 years while in men the estimated lifetime risk is about 73 percent. While most hereditary family cancer syndromes involve specific tumor types, members of LFS are at risk for a wide range of malignancies, with particular occurrences of breast cancer, bone sarcomas, and soft tissue sarcomas. Several other cancers have been reported but at a lower incidence in Li-Fraumeni syndrome.
Risk of developing multiple primary cancers is high in members of Li-Fraumeni syndrome families compared to the general population. This excess risk mainly involving cancers characteristic of LFS, this risk is further increased in survivors of childhood cancers, and these patients require close monitoring for early cancer signs.
Patients with LFS are successfully treated during the initial cancer occurrence. However, radiation therapy should be avoided, when possible, due to several case reports and preclinical evidence showing an increased risk of radiation-induced cancers in these patients. Li-Fraumeni patients are at a high risk of developing a second primary malignancy.
LI-Fraumeni syndrome (LFS) occurs due to germ-line mutations in TP53. TP53 is a tumor suppressor gene, which is located on band 17p13.1, codes for a 53-kD nuclear protein transcription factor that has important regulatory control over cell proliferation and homeostasis, specifically apoptosis, DNA repair, and cell cycle. Mutations can arise in one of the parent's germ cells, de novo during embryogenesis or can be inherited. Changes in P53 function results from either increased or aberrant protein function or loss of function of wild-type P53. Most Li-Fraumeni Syndrome TP53 mutations occur as missense point mutations in a hot-spot region of exons 5-8; this is the gene portion that codes for the core DNA-binding domain of the protein. This kind of mutation leads to stable but inactive protein, which accumulates in the nucleus of tumor cells. Any mutation like frameshift, nonsense, and splice-site can also be present but do not lead to accumulation of p53 protein.
Cell loses protection against genetic alterations when P53 mutations occur. Ubiquitin ligase HDM2 and P53 interact with E3 and E4 proteins, which induces polyubiquitination and degradation of P53., this prevents apoptosis. They also associate with overexpression of UBE4B with amplification of these genes in brain tumors. The absence of P53 mutations in some families indicate that P53 protein may undergo posttranslational modifications, or other genes may be involved. Genetic copy number variation, used as an indicator of genetic instability, are higher in patients with germline TP53 mutations than in healthy individuals.
Mutations Associated with Younger Age of Onset in Li-Fraumeni Syndrome
The family history of cancer, young age at initial diagnosis, and multiple malignancies suggest cancer syndromes which are hereditary. Patients should be informed adequately about all the signs and symptoms of cancer. They must be counseled to consult whenever they have any unusual signs or symptoms related to cancer. A complete family history of multiple generations is very important because of a significant increase in cancer risk within families. The history should include screening for multiple tumor types especially sarcomas, breast, leukemia, and adrenocortical tumors. Sometimes risk becomes evident only after several years, so it is very important to update the family history regularly. Obtaining a thorough family history can be difficult, but it is an important part of evaluating every child diagnosed with an early malignancy. History should emphasize all cancers in Li-Fraumeni syndrome spectrum.
No specific physical findings are seen in individuals affected by Li-Fraumeni syndrome that differ from the findings related to specific cancers. Physical findings to watch for in specific cancers:
An annual physical examination should be performed, including breast, skin and neurological assessments.
The patient should be trained to self-examine breast regularly every month, starting at age 18 years.
Initially, the diagnosis of Li-Fraumeni was done using clinical criteria based on signs and symptoms the patient and family have. With advanced genetic testing, people can now know if they carry a copy of TP53 tumor mutation before showing any signs of LFS. Genetic testing for TP53 mutations is very important. It is important to offer genetic counseling and testing to all relatives at risk of having a familial TP53 pathogenic variant. Genetic testing only detects approximately 70% to 75% of cases. Genetic counseling must be done to consider genetic testing, and if it concludes that a person is carrying a copy of TP53 mutations, the patient must be counseled about surveillance and continuously screen them for LFS related types of cancer.
The decision to do genetic counseling and TP53 mutation testing should be considered for the following patients:
Classic Li-Fraumeni syndrome - It is diagnosed when the person has all the following criteria:
This includes brain tumor, adrenocortical cancer, breast cancer in the proband and also has a lower age cutoff of <31 years. Consider a diagnosis of LFS for anyone with a personal and family history that meets one of the following three criteria.
Li-Fraumeni-like syndrome (LFL) is another criteria for families who do not meet the set classic criteria.
LFL-1, Birch Definition
LFL-2, ELES Criteria
Two relatives (first-degree or second-degree) diagnosed with a typical LFS cancer at any age.
Individuals with some cancers irrespective of age or family history should undergo genetic testing for TP53 deleterious gene mutations. These include a) adrenocortical carcinoma b) choroid plexus carcinoma at any age c) rhabdomyosarcoma before age three years d) osteosarcoma before age ten years e) childhood sarcoma (except Ewing's sarcoma).
Cancer surveillance is required for individuals who are at risk based on the history of LFS malignancy, the patient with known TP53 tumor mutation, or those with increased risk in a family with LFS but without an identifiable mutation or who have not undergone mutation testing.
There is currently no procedure or treatment option to fix mutations in the P53 gene as P53 is not a drug target yet. In general radiation, therapy should be avoided in patients with Li-Fraumeni syndrome because individuals are at high risk of radiation-induced secondary cancers. Similarly, exposure to CT scans or X-rays should be avoided. Li-Fraumeni syndrome is a complex syndrome with many implications for individuals and their families, so it is suggested patients with LFS or suspected LFS consult with a physician or hospital that has experience in treating patients with Li-Fraumeni Syndrome and providing the medical care, genetic counseling, and special support services.
No evidence suggests that individuals with LFS diagnosed with cancers should be treated uniquely from other patients with the same cancer. However, in breast cancer, complete mastectomy rather than lumpectomy which is usually followed by radiation therapy is generally preferred because of the risks of second breast cancers or radiation-induced neoplasms. Physicians should discuss the need for risk-reducing mastectomy; it must be considered case-by-case, depending on the degree of cancer risk and reconstructive options.
Li-Fraumeni syndrome patients are prone to anxiety, depression, and clinically relevant distress. Psychological monitoring is important and providing support is very important.
There is no difference in the treatment of cancers in LFS and other cancers which occur sporadically. Advancement in the treatment of childhood cancers has increased the long-term survival for most children. Usual complications in survivors include second primary malignancies, which mostly occur within 6 to 12 years after the first cancer.
A second cancer may occur due to genetic predispositions such as constitutional TP53 mutations. The risk for a second cancer increases with younger age at diagnosis of first cancer. Second cancer risk increases with radiation exposure, so these individuals should avoid or minimize exposure to diagnostic and therapeutic radiation when possible. They have a predilection for developing subsequent primary tumors (especially sarcomas) in prior radiation fields.
The cumulative probability of a person affected by LFS developing a second cancer is close to 60% at 30 years after developing first cancer.
Individuals with Li-Fraumeni syndrome can become resistant to chemotherapy. Risk of other primary cancers is increased if a germline mutation has occurred. There is evidence that a TP53 genetic mutation can cause a person to have an increased sensitivity to ionizing radiation. Individuals with germline TP53 mutations should avoid or minimize exposure to diagnostic and therapeutic radiation when possible.