What are BRCA1 and BRCA2?
BRCA1 and BRCA2 are human genes that produce tumor suppressor proteins. These proteins help repair damaged DNA and, therefore, play a role in ensuring the stability of the cell’s genetic material. When either of these genes is mutated, or altered, such that its protein product is not made or does not function correctly, DNA damage may not be repaired properly.
As a result, cells are more likely to develop additional genetic alterations that can lead to cancer. Specific inherited mutations in BRCA1 and BRCA2 increase the risk of female breast and ovarian cancers, and they have been associated with increased risks of several additional types of cancer. Together, BRCA1 and BRCA2 mutations account for about 20% to 25% of hereditary breast cancers1 and about 5% to 10% of all breast cancers.2 In addition, mutations in BRCA1 and BRCA2 account for around 15% of ovarian cancers overall.3
Breast cancers associated with BRCA1 and BRCA2 mutations tend to develop at younger ages than sporadic breast cancers. A harmful BRCA1 or BRCA2 mutation can be inherited from a person’s mother or father. Each child of a parent who carries a mutation in one of these genes has a 50% chance of inheriting the mutation. The effects of mutations in BRCA1 and BRCA2 are seen even when a person’s second copy of the gene is normal.
How much does having a BRCA1 or BRCA2 gene mutation increase a woman’s risk of breast and ovarian cancer?
A woman’s lifetime risk of developing breast and/or ovarian cancer is greatly increased if she inherits a harmful mutation in BRCA1 or BRCA2. Breast cancer: About 12% of women in the general population will develop breast cancer sometime during their lives.4 By contrast, according to the most recent estimates, 55% to 65% of women who inherit a harmful BRCA1 mutation and around 45% of women who inherit a harmful BRCA2 mutation will develop breast cancer by age 70 years.5,6
Ovarian cancer: About 1.4% of women in the general population will develop ovarian cancer sometime during their lives.4 By contrast, according to the most recent estimates, 39% of women who inherit a harmful BRCA1 mutation5,6 and 11% to 17% of women who inherit a harmful BRCA2 mutation will develop ovarian cancer by age 70 years.5,6
It is important to note that these estimated percentages of lifetime risk are different from those available previously; the estimates have changed as more information has become available, and they may change again with additional research. No long-term general population studies have directly compared cancer risk in women who have and do not have a harmful BRCA1 or BRCA2 mutation.
It is also important to note that other characteristics of a particular woman can make her risk higher or lower than the average risks. These characteristics include her family history of breast, ovarian, and, possibly, other cancers; the specific mutation(s) she has inherited; and other risk factors, such as her reproductive history. However, none of these other factors is as strong as the effect of carrying a harmful BRCA1 or BRCA2 mutation.