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BRCA mutation testing overview

Published: April 01, 2017. Updated: April 09, 2017

The BRCA gene test is used to identify mutations in either one of the two breast cancer susceptibility genes, BRCA1 and BRCA2. Women who have inherited mutations in these genes are at an increased risk of developing breast cancer and ovarian cancer compared with the general population.

Because genetic tests are associated with potential risks including psychological, financial, legal, social and medical risks, it is critical that candidates undergo pre-test evaluation of genetic risk by a board-certified genetic counselor as well as post-test counseling to review the results as well as the options. Unfortunately, despite an increase in the rate of women getting tested in the U.S., too few women are receiving genetic counseling.

Indications

Genetic testing for BRCA mutation is mainly indicated in patients with cancer who are at high risk of having an underlying BRCA mutation but also to a limited extent in individuals who do not have cancer when an affected family member is not available. BRCA1/2 mutations affect homologous DNA repair, therefore affected individuals are themselves at higher risk of developing cancer. BRCA1/2 mutations produce hereditary breast-ovarian cancer syndrome (HBOC) in affected persons, and therefore affects individuals at a young age. Because mutations in BRCA1 and BRCA2 are inherited in an autosomal dominant manner, they exhibit high penetrance, meaning there’s usually a strong family history.

As a result patients who should be screened are characterized by:

  1. young age at diagnosis due to hereditary nature (≤45 years or ≤50 years plus additional risk factors, ≤60 years with triple negative breast cancer)
  2. susceptibility due to mismatch-repair (2 or more primary breast cancers, HBOC-associated cancers)
  3. high penetrance due to autosomal dominant inheritance (family history) or Ashkenazi ancestry.

Testing in the general population

BRCA1 and BRCA2 mutations are relatively rare in the general population. As a result, the USPSTF recommends using one of several screening tools to identify women in the general population whose personal or family history is suggestive of an increased risk of BRCA1/2 mutations. Women with positive screening results should receive genetic counseling and, if indicated after genetic counseling, BRCA testing. These include women with:

  • A known BRCA1 or BRCA2 mutation within the family
  • A family history pattern suggestive of hereditary cancer (multiple relatives with breast, ovarian, tubal, or peritoneal cancer; single relative with both breast and ovarian cancer; relatives diagnosed at young age; Ashkenazi Jewish ancestry; male breast cancer)

When an individual has a family history that is suggestive of the presence of a BRCA1 or BRCA2 mutation, it may be most informative to first test a family member who has cancer if that person is still alive and willing to be tested. If that person is found to have a harmful BRCA1 or BRCA2 mutation, then other family members may want to consider genetic counseling to learn more about their potential risks and whether genetic testing for mutations in BRCA1 and BRCA2 might be appropriate for them.

For a more comprehensive list of indications please refer to the National Comprehensive Cancer Network Guidelines [1].

 

 


References



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