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Genetic Examination of Inherited Cancer (BRCA1, BRCA2)

Genetic Examination of Inherited Cancer (BRCA1, BRCA2)

The various types of cancer are the main cause of morbidity and mortality in the world population. The most common type of cancer that occurs between women worldwide is breast cancer. The disease can occur in any woman in the population in a frequency of 12%. However, among women who suffer from breast cancer, a rate of 5-10% is considered to be of genetic causes. Therefore, a hereditary type of breast cancer is responsible for these cases.

The hereditary type of breast cancer is associated with mutations occurring in the BRCA1 and BRCA2 genes. These genes belong to the tumor suppressor genes. Normally, their role is to prevent the development of tumors. However, due to various mutations that may occur in these genes, their normal function can be altered, resulting in risk of developing breast and ovarian cancer, as well as other types of cancer.
The occurring mutations may vary and affect the risk of cancer to different degrees. Therefore, a woman carrying mutations in BRCA1 and BRCA2 genes does not mean that she will definitely develop cancer. However, she has an increased risk of showing cancer, compared to another woman.

Examination can be done by specific genetic tests that are able to determine the mutations in the two related genes. The test is performed by isolating genetic material from blood cells.

Since BRCA gene mutations are relatively rare in the general population, only individuals with a family history are recommended to perform the genetic test.

Genetic testing is recommended in the following cases:
– women diagnosed with breast cancer in age less than 45 years, regardless of history
– when at least two relatives of 1st- 3rd degree are diagnosed with breast, ovarian or pancreatic cancer irrespective of age, irrespectively of the age.
– when a relative of 1st -3rd degree is diagnosed with male breast cancer
– bilateral breast cancer in the same woman
– diagnosis of breast and ovarian cancer in the same woman or in a relative of the same family
– Multiple cases of breast cancer within the same family

The result of the gene examination may be positive, negative or uncertain. A positive result means that a known mutation of the BRCA genes has been identified. This mutation has been inherited and it is associated with an increased risk of developing various forms of cancer. However, the identification of such a mutation does not mean that this woman will definitely develop cancer in her life, but the positive result indicates that this woman is more likely to show cancer compared to another woman.
Indeed, there are female carriers of BRCA1 and BRCA2 gene mutations that will never develop breast or ovarian cancer in their lives. However, carriers of a mutated gene have 50% chance of inheriting it to their children, even if they are not affected.

In case of a negative result regarding the existence of mutations in the BRCA1 and BRCA2 genes, then it could be interpreted based on the family medical history of each individual. The validity of a negative result can be assessed by the existence of a family member which carry a known mutation in these genes.
Additionally, the degree of affinity with this individual may indicate the certainty of the results or the possibility that this person may carry a new mutation- not previously described.

A result may be described as uncertain in the case that a mutation in the BRCA genes is identified, but it considered of dubious effect. This is because this mutation may not already be linked in the past with incidents of cancer, or if it has not been clarified yet
An uncertain result, a mutation in the BRCA genes can be described as uncertain, as it is unlikely to have been previously associated with the incidence of cancer, and it has not been elucidated whether it is a deleterious change in the genetic material.

Individuals performing the BRCA gene examination are advised to receive appropriate genetic counseling both before and after the genetic analysis. The geneticist is able to clarify any questions about the screening process and its necessity, can interpret the results of the test, and the possibility of delivering a mutation to the next generation.