The BRCA GENE
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 andovarian 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 percent ofhereditary breast cancers (1) and about 5 to 10 percent of all breast cancers (2). In addition, mutations in BRCA1 and BRCA2 account for around 15 percent 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 percent 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 percent 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 percent of women who inherit a harmful BRCA1 mutation and around 45 percent of women who inherit a harmful BRCA2 mutation will develop breast cancer by age 70 years (5, 6).
Ovarian cancer: About 1.4 percent of women in the general population will develop ovarian cancer sometime during their lives (4). By contrast, according to the most recent estimates, 39 percent of women who inherit a harmful BRCA1 mutation (5, 6) and 11 to 17 percent 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 studieshave directly compared cancer risk in women who have and do not have a harmful BRCA1 orBRCA2 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.
Because harmful BRCA1 and BRCA2 gene mutations are relatively rare in the general population, most experts agree that mutation testing of individuals who do not have cancer should be performed only when the person’s family history suggests the possible presence of a harmful mutation in BRCA1 or BRCA2.
- Multiple breast and/or ovarian cancers within a family (often diagnosed at an early age)
- Two or more primary cancers in a single family member (more than one breast cancer, or breast and ovarian cancer)
- Cases of male breast cancer
In a family with one of these cancer history patterns, it may be most informative to first test a family member who has breast or ovarian 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.
Even if it is not possible to confirm the presence of a harmful BRCA1 or BRCA2 mutation in a family member who has cancer, women with a family medical history that suggests the presence of such a mutation may also want to consider genetic counseling and possible testing.
Several professional organizations and expert groups, such as the United States Preventive Services Task Force, have developed clinical criteria that can be helpful to health care providers in identifying individuals for whom BRCA1 or BRCA2 mutation testing may be appropriate (15).
Some women—for example, those who were adopted at birth—may not know their family history. If a woman with an unknown family history has an early-onset breast cancer or ovarian cancer, it may be reasonable for her to consider genetic testing for a BRCA1 or BRCA2mutation. Women with an unknown family history and who do not have an early-onset cancer, even if they think they have an Ashkenazi Jewish background, are at very low risk of having a harmful BRCA1 or BRCA2 mutation and are unlikely to benefit from genetic testing.
Professional societies do not recommend that children, even those with a family history suggestive of a BRCA1 or BRCA2 mutation, undergo genetic testing. This is because no risk-reduction strategies for children exist, and their risk of developing a cancer type associated with a BRCA1 or BRCA2 mutation is extremely low. After they become adults, however, they may want to obtain genetic counseling about whether or not to undergoing genetic testing.
Key points about the BRCA gene:
- A woman’s risk of developing breast and/or ovarian cancer is greatly increased if she inherits a deleterious (harmful) mutation in the BRCA1 gene or the BRCA2 gene.
- Men with these mutations also have an increased risk of breast cancer, and both men and women who have harmful BRCA1 or BRCA2 mutations may be at increased risk of additional types of cancer.
- Genetic tests can check for BRCA1 and BRCA2 mutations in people with a family history of cancer that suggests the possible presence of a harmful mutation in one of these genes.
- If a harmful BRCA1 or BRCA2 mutation is found, several options are available to help a person manage their cancer risk
read more here
Please open the first graph in a new tab or window to view full size