Many women may wonder what genetic testing would reveal about their own risks for cancer. Learn more about the BRCA mutations and guidelines for genetic testing.
About BRCA1 and BRCA2
Both BRCA1 (on chromosome 17) and BRCA2 (on chromosome 13) are human genes that all people have, and, when functioning normally, produce proteins that help repair damaged DNA and maintain the cell’s genetic stability.
However, if either gene is mutated or altered, these proteins either aren’t made or fail to function correctly, which can prevent DNA damage from being repaired. This can increase the risk of the cells developing additional genetic alterations that can lead to cancer.
Cancers linked to BRCA1 and BRCA2 mutations
According to the National Cancer Institute, female breast and ovarian cancers (both hereditary and non-hereditary), have been linked to specific mutations in BRCA1 and BRCA2. Approximately 5-10% of breast cancers and 10-15% of ovarian cancers are caused by genetic mutations within a person’s genes, including, but not limited to, BRCA1 and BRCA2.
Lifetime risks for developing breast cancer for those who have inherited BRCA1 and BRCA2 mutations include:
- 55-72% of women with the inherited BRCA1 mutation will develop breast cancer by age 70-80.
- 45-69% of women with the inherited BRCA2 mutation will develop breast cancer by age 70-80.
The risk for developing ovarian cancer is lower but still important to monitor. Lifetime risks are as follows:
- 39-44% of women with the inherited BRCA1 mutation will develop ovarian cancer by age 70-80.
- 11-17% of women with the inherited BRCA2 mutation will develop ovarian cancer by age 70-80.
These risks are significantly higher than risks for the population in general, where it’s estimated that approximately 13% of women will develop breast cancer sometime in their lives and 1.2% of women will develop ovarian cancer.
Among men, the general population has a lifetime risk for developing breast cancer of less than 1%, but that risk increases to 7% with BRCA2 mutation and 1% with BRCA1 mutation. Men with a BRCA1 mutation have an increased risk of prostate cancer as high as 9% by age 65. Men with a BRCA2 mutation have an increased risk of prostate cancer as high as 33% by age 65.
Persons with BRCA1 and BRCA2 mutations are also at an increased risk for pancreatic cancer, with a risk of 1% for BRCA1 mutations and nearly 5% for BRCA2 mutations.
Risk factors for BRCA mutations
Certain factors can increase the risk of carrying a BRCA mutation:
- Genetics – If either parent carries the BRCA mutation, the child has a 50 percent chance of inheriting the mutation. If any person (for example, a cousin, grandparent) in the family has a known mutation, testing may be a consideration. However, the gene does not skip generations, so if a family member has confirmed negative testing, their children do not need to worry.
- Ethnic origins – Statistically speaking, persons of Ashkenazi Jewish descent, as well as Norwegian, Dutch, and Icelandic nationalities, are more likely to have BRCA1 or BRCA2 mutations.
- Family history – Having first or second-degree relatives with breast or ovarian cancer, male breast cancer, or pancreatic cancer can increase the likelihood of the presence of the BRCA1 or BRCA2 mutations.
Genetic testing for BRCA mutations
The United States Preventive Services Task Force has made the following recommendation for women considering genetic testing for BRCA mutations:
- Women who have a personal or family history of breast, ovarian, tubal, or peritoneal cancer, or an ancestry associated with BRCA1/2 should be screened to see if their history is associated with an increased risk of carrying a BRCA mutation. If so, then genetic counseling is recommended to determine if BRCA testing would be useful.
- Women whose personal or family history or ancestry is not associated with increased risk for BRCA mutations do not need routine genetic counseling or BRCA testing.
Not all genetic testing is created equal! For example, while 23andMe looks at the BRCA1 and BRCA2 gene, the assay only detects three variants, which misses approximately 90% of the BRCA mutations that can cause cancer. A person should always review planned genetic testing with their care team.
Several different types of genetic testing methods are available to detect the BRCA mutations – some look for the mutations in one of the genes and others check for all possible mutations in both genes. The samples for testing typically involve DNA extracted from blood or saliva, and it usually takes about one month for results.
Certain Sarah Cannon facilities offer cancer genetic risk assessments and genetic counseling to women who have concerns about their personal and/or family history of cancer. Patients are provided with personalized information regarding hereditary risk, specific cancer risks, and targeted screening and prevention options.