Adjusting the estimated proportion of breast cancer cases associated with BRCA1 and BRCA2 mutations: public health implications

Genet Med. 2005 Jan;7(1):28-33. doi: 10.1097/01.gim.0000151155.36470.ff.


Purpose: Mutations in BRCA1 or BRCA2 genes increase breast cancer risk. Assuring reliability of information about these mutations is increasingly important to the health care community; mutation testing is becoming more widespread. We describe a methodology for assessing such information.

Methods: Our approach integrates four interdependent epidemiologic parameters: (1) the probability of developing breast cancer, (2) the proportion of breast cancer cases with a BRCA1 or BRCA2 mutation, (3) the proportion of women that carries a mutation, and (4) the proportion of women with a mutation that develops cancer. We assess the plausibility of estimates of these parameters from published reports and commonly accessed information sources.

Results: Assuming a fixed probability of developing breast cancer, the following estimates for the other three epidemiologic parameters are derived for women by age 70: 1% to 2% of all breast cancer cases are associated with a BRCA1 or BRCA2 mutation; 1 in 300 to 1 in 465 women carry a mutation; and 35 to 65% of mutation carriers develop breast cancer. Within these ranges, however, only selected combinations are plausible. The proportion of mutation-related breast cancer is lower than listed in some common information sources (1 to 2% vs 6%). Also, penetrance is somewhat lower and the carrier rate somewhat higher.

Conclusions: The four epidemiologic parameters can be integrated to test their plausibility. BRCA1 and BRCA2 mutations are associated with only one-third as many breast cancer cases in the general population as reported by commonly accessed information sources.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • BRCA1 Protein / genetics*
  • BRCA2 Protein / genetics*
  • Breast Neoplasms / epidemiology*
  • Breast Neoplasms / genetics
  • Female
  • Genetic Predisposition to Disease / epidemiology*
  • Genetic Predisposition to Disease / genetics
  • Genetic Testing
  • Humans
  • Middle Aged
  • Mutation*
  • Neoplasm Proteins / genetics*
  • Penetrance
  • Prevalence
  • Risk Factors


  • BRCA1 Protein
  • BRCA2 Protein
  • Neoplasm Proteins