What is the prevalence of BRCA1 and BRCA2 mutations in breast cancer?

Updated: Dec 16, 2019
  • Author: Jessica Katz, MD, PhD, FACP; Chief Editor: Marie Catherine Lee, MD, FACS  more...
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Answer

Answer

The BRCA1 and BRCA2 gene mutations, on chromosomes 17 and 13, respectively, account for the majority of autosomal dominant inherited breast cancers. Both genes are believed to be tumor suppressor genes whose transcribed protein products are involved with maintaining DNA integrity and transcriptional regulation.

Prevalence rates of these mutations vary by ethnic and racial groups. For BRCA1 mutations, the highest rates occur among Ashkenazi Jewish women (8.3%), followed by Hispanic women (3.5%), non-Hispanic white women (2.2%), black women (1.3%), and Asian women (0.5%). Moreover, 95% of Ashkenazi Jews with a BRCA gene mutation will have 1 of the 3 founder mutations (185delAG, 538insC in BRCA1; 6174delT in BRCA2). Women who inherit a mutation in the BRCA1 or BRCA2 gene have an estimated 50-80% lifetime risk of developing breast cancer. 

BRCA1 mutations are seen in 7% of families with multiple breast cancers and 40% of families with breast and ovarian cancer. Women with a BRCA1 mutation have a 40% lifetime risk of developing ovarian cancer. Breast cancers that develop in BRCA1 mutation carriers are more likely to be high grade, as well as estrogen receptor (ER) negative, progesterone receptor (PR) negative, and HER2-negative (triple negative) or basal-like subtype. BRCA1 mutations are also associated with a higher risk of colon, pancreatic, and prostate cancer. [14]

BRCA2 mutations are identified in 10-20% of families at high risk for breast and ovarian cancers but in only 2.7% of women with early-onset breast cancer. Women with a BRCA2 mutation have an approximately 10% lifetime risk of ovarian cancer. BRCA2 mutation carriers who develop breast cancer are more likely to have a high-grade, ER-positive, PR-positive, and HER2-negative cancer (luminal type). BRCA2 is also a risk factor for male breast cancer. Other cancers associated with BRCA2 mutations include the following [15] :

  • Prostate
  • Pancreas
  • Gallbladder and bile duct
  • Stomach
  • Malignant melanoma

The US Preventive Services Task Force (USPSTF) recommends that women who have family members with breast, ovarian, tubal, or peritoneal cancer should be screened to identify a family history that may be associated with an increased risk for carriage of BRCA1 or BRCA2. For women with positive screening results, the USPSTF recommends genetic counseling and, if indicated after counseling, BRCA testing. [16]


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