What are BRCA1 and BRCA2?
BRCA1 and BRCA2, or breast cancer gene 1 and breast cancer gene 2, are both genes responsible for producing proteins that repair damaged DNA. Their gene-products fix DNA so that cancer does not develop. For this reason, they are often referred to as “tumor suppressing genes.”
We all have two copies of each of these genes, one inherited from each parent. For some patients, one or both copies of the BRCA1 or BRCA2 may have a harmful variant, otherwise known as a pathogenic variant or mutation. This means that cancer is more likely to develop. Harmful variants in BRCA1 and BRCA2 are most closely associated with breast cancer and ovarian cancer, but other types of cancer can also result from this mutation.
How Much Does a Harmful Variant in BRCA1 or BRCA2 Increase Risk of Breast or Ovarian Cancer?
If you inherit a harmful variant in either the BRCA1 or BRCA2 gene, your risk of breast or ovarian cancer increases significantly. In the general population, about 13% of women develop breast cancer at some point in their lifetime. However, about 40-87% of those with a mutation in the BRCA1 gene will develop breast cancer, and 45-69% of those with a mutation in the BRCA2 gene develop breast cancer. Individual risk will vary depending on other genetic factors and environmental exposures.
Only about 1.2% of women in the general population develop ovarian cancer in their lifetime. However, this number increases to 39-44% of those with a BRCA1 mutation and 11-17% for those with a BRCA2 mutation.
Breast and ovarian cancers are not the only cancers that patients with these gene variants may face. BRCA1 and BRCA2 gene variants increase the risk of fallopian tube cancer, primary peritoneal cancer, pancreatic cancer, and melanoma. Men who inherit a harmful variant are also at a higher risk for prostate and male breast cancer. Finally, children who inherit two BRCA2 mutations are at a higher risk for childhood solid tumors, acute myeloid leukemia, and Fanconi anemia.
Are Harmful Variants in BRCA1 and BRCA2 More Common in Certain Racial/Ethnic Populations?
Harmful variants of BRCA1 and BRCA2 genes are more common among certain racial or ethnic groups. This includes those of Ashkenazi Jewish and African American decent in particular. Many people within these groups carry unique variants not found in other racial or ethnic groups. This is true of African American BRCA1 variants. Other groups have been found to carry specific variants known as founder mutations. This applies to Ashkenazi Jewish, Norwegian, Dutch, and Icelandic people. However, it is important to remember that patients outside of these groups can still be at a higher risk for cancer because of inherited genetic variations. If you have other signs of a higher cancer risk running in your family, your genetic counselor may still recommend testing regardless of your racial or ethnic background.
Who Should Consider Genetic Counseling or Testing for BRCA1 and BRCA2 Variants?
Anyone who has concerns that cancer may run in their family should pursue genetic counseling. Your genetic counselor can determine whether it would be beneficial for you to test for BRCA1 and BRCA2 variants based on factors like your racial and ethnic background, your personal or family history of cancer, whether your relatives have known BRCA1 or BRCA2 variants, and more. This is done through a risk assessment with your genetic counselor, after which you can discuss benefits or potential harms of receiving genetic testing.
If you do decide to move forward with genetic testing for BRCA1 and BRCA2 variants, this can help you make healthcare choices to prevent cancer or detect cancer early. If you do develop cancer and have a known BRCA1 or BRCA2 variant, this can help determine an appropriate treatment option. Testing for these variants is done by analyzing blood or saliva samples. At-home tests are available for consumers, but it is best to work with a genetic counselor who can help you determine who would be the most appropriate family member to test, if and when testing is beneficial, what genes to test for, and how to interpret the results.
Testing is not recommended for every adult for several reasons. It may present unnecessary stress for some patients. Waiting to hear your test results or receiving news that you have a BRCA1 or BRCA2 gene mutation can be a significant source of anxiety for many. In addition, genetic testing is often expensive and might be considered an unnecessary cost for those who have particularly low risk. Other members of your family might actually be better candidates than you for this testing. For these reasons, your genetic counselor may recommend that you do not move forward with testing. In the end, the decision is yours to make.
What do BRCA1 and BRCA2 Genetic Test Results Mean?
There are three basic options for BRCA1 and BRCA2 mutation testing: positive results, negative results, or inconclusive (variant of uncertain significance, or VUS) results.
Positive results from a BRCA1 and BRCA2 genetic test means that you do have a known harmful variant in BRCA1 or BRCA2. In your lab results, this may be marked as “pathogenic” or “likely pathogenic.” This means that you do have an increased risk for developing breast cancer, ovarian cancer, or other types of cancers. It is important to remember, however, that not all patients who have these harmful variants will develop cancer; you are simply at a higher risk.
If you receive positive results from BRCA1 or BRCA2 genetic tests, this means that your close blood relatives also have a higher risk of having the variants. For example, your full siblings have a 50% chance of having the inherited variant. If this is the case, it may be in their best interest to visit a genetic counselor as well.
A negative result from a BRCA1 and BRCA2 genetic test means that you do not have a harmful variant and are not at a higher risk for developing cancer due to your genetics. You might still be considered to have an increased risk for cancers due to other factors such as your family history and personal medical history. This will be explained to you by your doctors. Always remember that lifestyle or environmental factors can still increase your risk, despite having no BRCA1 or BRCA2 mutations. For this reason, it is still important to have routine screenings as recommended by your doctor and maintain a healthy lifestyle.
Inconclusive, or “variant of uncertain significance” results mean that there is a change or mutation in your BRCA1 or BRCA2 genes, but it is not presently known if this change is benign or harmful. Additional data and research is necessary to understand the significance of these variants and whether they present a risk. Your genetic counselor can help you interpret these results and what they mean for your health.
How Can Someone Who Has a Harmful BRCA1 or BRCA2 Gene Variant Reduce Risk of Cancer?
If you have been found to have a harmful BRCA1 or BRCA2 gene variant, there are several steps you can take to reduce your risk of cancer and increase the chances of detecting cancer early. Prevention is the primary goal. In addition, early detection is very important in improving the effectiveness of cancer treatment.
Patients with BRCA1 and BRCA2 mutations start mammograms at an earlier age and also get breast MRI to improve detection of early-stage breast cancer.
What are the Benefits of Genetic Testing for BRCA1 and BRCA2 Variants?
The primary benefit of genetic testing for BRCA1 and BRCA2 gene variants is that testing allows you to be proactive and make informed decisions regarding your healthcare. It can help you and your doctors determine how frequently you should receive cancer screening tests or make other changes to prevent or detect certain types of cancer. Receiving negative results can also help patients relieve some stress. During a consultation, your provider will help you decide whether genetic testing would be beneficial for you.