The BRCA gene test is a blood test that uses DNA analysis to identify harmful changes (mutations) in either one of the two breast cancer susceptibility genes — BRCA1 and BRCA2.
People who inherit mutations in these genes are at an increased risk of developing breast cancer and ovarian cancer compared with the general population.
The BRCA gene test is offered to those who are likely to have an inherited mutation based on personal or family history of breast cancer or ovarian cancer. The BRCA gene test isn't routinely performed on people at average risk of breast and ovarian cancers.
The results of genetic testing aren't always clear. A positive result means you carry a gene mutation that increases your risk of cancer and you can work with your doctor to manage that risk. A negative result may mean that you don't have the mutation or that you might have a gene mutation doctors haven't discovered yet. Your test might also identify a gene variant that doctors aren't certain about. In these situations, it's not always clear what the results mean for your cancer risk.
Most people considering genetic testing undergo genetic counseling. Genetic counseling can help you understand what the results could mean for your health, help you decide whether genetic testing is right for you, and recommend a specific set of genetic tests based on your family history.
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Why it's done
The BRCA gene test is a blood test that's done to determine if you have changes (mutations) in your DNA that increase the risk of breast cancer.
Mutations in either breast cancer gene — BRCA1 or BRCA2 — significantly increase the risk of:
- Breast cancer
- Male breast cancer
- Ovarian cancer
- Prostate cancer
- Pancreatic cancer
If a gene mutation is detected, you and your doctor can work together to manage your risk.
Who should consider BRCA gene testing?
You might be at increased risk of having an inherited gene mutation that increases the risk of breast and ovarian cancers — and a candidate for genetic testing — if you have:
- A personal history of breast cancer diagnosed before age 45
- A personal history of breast cancer diagnosed before age 50 and a second primary breast cancer, one or more relatives with breast cancer, or an unknown or limited family medical history
- A personal history of triple negative breast cancer diagnosed at age 60 or younger
- A personal history of two or more types of cancer
- A personal history of ovarian cancer
- A personal history of male breast cancer
- A personal history of breast cancer and one or more relatives with breast cancer diagnosed before age 50, two or more relatives diagnosed with breast cancer at any age, one or more relatives with ovarian cancer, one or more relatives with male breast cancer, or two or more relatives with prostate cancer or pancreatic cancer
- A personal history of breast cancer and Ashkenazi (Eastern European) Jewish ancestry
- A personal history of prostate cancer or pancreatic cancer with two or more relatives with BRCA-associated cancers
- A history of breast cancer at a young age in two or more blood relatives, such as your parents, siblings or children
- A relative with a known BRCA1 or BRCA2 mutation
- One or more relatives with a history of cancer that would meet any of these criteria for gene testing
Ideally, in a family that might carry a gene mutation, a family member who has breast or ovarian cancer will have the BRCA gene test first. If this individual agrees to genetic testing and doesn't carry the BRCA gene mutation, then other family members may not benefit from genetic testing. However, there might be other genetic tests to consider. A genetic counselor can help you decide what other genetic testing options may be available based on your personal and family history.
Other breast cancer genes
Researchers have identified mutations in multiple genes that increase the risk of breast cancer. Your doctor might recommend testing for these gene mutations, too, based on your family history of cancer.
- Breast cancer
- Ovarian cancer
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There's no medical risk associated with being tested for a BRCA gene mutation other than the slight risks — including lightheadedness, bleeding or bruising — of having your blood drawn. Other consequences surrounding genetic testing include the emotional, financial, medical and social implications of your test results.
If you test positive for an inherited genetic mutation, you may face:
- Feelings of anxiety, anger, sadness or depression
- Concerns over possible insurance discrimination
- Strained family relationships over learning of a familial genetic mutation
- Difficult decisions about preventive measures that have long-term consequences
- Feelings of inevitability that you'll get cancer
On the other hand, if you test negative for a BRCA mutation or your results aren't clear-cut — for example, you have a genetic variation, but one that hasn't been associated with cancer in other people — you may experience:
- "Survivor guilt" if your family has a known gene mutation that may affect your loved ones (if you receive a negative result)
- Uncertainty and concern that your result may not be a true negative result (if your results show you have a gene variant of uncertain significance)
Your genetic counselor can help you work through your feelings and provide you and your family support throughout this process.
How you prepare
The first step in the BRCA gene testing process is to meet with a genetic counselor. As soon as you consider having any genetic test, meet with a genetic counselor to determine whether it's appropriate for you and to discuss the potential risks, limitations and benefits of undergoing genetic testing.
The genetic counselor takes a detailed family and medical history, assesses your risk of developing cancer, discusses risks and benefits of genetic testing, and outlines your options.
To prepare for your meeting with a genetic counselor:
- Gather information about your family's medical history, especially that of close relatives.
- Document your personal medical history, including collecting records from specialists or results of previous genetic testing, if available.
- Write down questions for the counselor.
- Consider having a friend or family member accompany you to help ask questions or take notes.
Whether to proceed with genetic testing after you meet with a genetic counselor is up to you.
If you decide to have BRCA genetic testing, prepare yourself for the emotional and social implications that learning your genetic status might have. Test results could also fail to provide you with clear-cut answers regarding your cancer risk, so prepare to face that possibility, too.
What you can expect
The BRCA gene test is most often a blood test. A doctor, nurse or medical technician inserts a needle into a vein, usually in your arm, to draw the blood sample needed for testing. The sample is sent to a lab for DNA analysis.
In some cases, other sample types are collected for DNA analysis, including saliva. If you have a family history of cancer and are interested in pursuing a saliva DNA test, discuss this with your doctor. He or she can refer you to a genetic counselor who can determine the most appropriate sample type for genetic testing.
It may take a few weeks before test results are available. You meet with your genetic counselor to learn your test results, discuss their implications and go over your options.
Your test results may be positive, negative or uncertain.
Positive test result
A positive test result means that you have a mutation in one of the breast cancer genes, BRCA1 or BRCA2, and therefore a much higher risk of developing breast cancer or ovarian cancer compared with someone who doesn't have the mutation. But a positive result doesn't mean you're certain to develop cancer.
Follow-up care after a positive test result might include taking specific measures to modify the type and frequency of screening for cancer and to consider procedures and medications designed to reduce your cancer risk. What you choose to do depends on many factors — including your age, medical history, prior treatments, past surgeries and personal preferences.
Negative or uncertain test result
A negative test result means that no BRCA gene mutation was found. However, assessing your cancer risk is still difficult. The test result is considered a "true negative" only if it finds that you don't carry a specific BRCA mutation that's already been identified in a relative.
A negative test result doesn't mean you definitely won't get breast cancer. You still have the same cancer risk as that of the general population.
An ambiguous result, also known as a variant of uncertain significance, occurs when the analysis finds a genetic variant that may or may not be associated with an increased risk of cancer. It is helpful to meet with your genetic counselor to understand how to interpret this finding and decide on appropriate follow-up.
New models are being developed to help determine risk of cancer with ambiguous results. Most variants of uncertain significance are eventually reclassified into either a positive or negative result. To be informed when this happens, stay in touch with the doctor or genetic counselor who ordered your genetic test.
Although the BRCA gene test can detect the majority of mutations in the BRCA1 and BRCA2 genes, you could have a gene mutation that the test wasn't able to detect. Or you may be at high risk of hereditary cancer if your family carries a high-risk gene mutation that researchers haven't yet identified. Finally, your family may have another hereditary cancer gene mutation that can be detected with other genetic tests.
Researchers are continuing to study gene mutations that increase the risk of cancer and developing new gene tests. If your gene test was done more than five years ago, your doctor might recommend testing again with newer tests. If your family health history changes, such as if additional family members develop cancer, your doctor might also recommend additional gene testing.
By Mayo Clinic Staff
Aug. 12, 2021