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.
Women who have inherited 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 only to people who are likely to have an inherited mutation based on personal or family history, or who have a specific type of breast cancer. The BRCA gene test isn't routinely performed on women at average risk of breast and ovarian cancers.
A BRCA gene test determines whether you carry an inherited BRCA mutation. If you do, your result is positive and your doctor can help you understand your cancer risk. If you don't have a mutation, this is considered a negative result. However, you may learn you have a gene variant that doctors aren't sure about. It may or may not be associated with an increased risk of breast and ovarian cancer. This result is known as a variant of uncertain significance.
Most people considering genetic testing undergo genetic counseling, which can help you understand what the results could mean for your health and help you decide whether genetic testing is right for you.
Why it's done
Having a BRCA gene mutation is uncommon. Inherited BRCA gene mutations are responsible for about 5 to 10 percent of breast cancers and about 15 percent of ovarian cancers.
Mutations to either breast cancer gene — BRCA1 or BRCA2 — significantly increase your risk of developing breast cancer and ovarian cancer when compared with the cancer risk of a woman without a BRCA gene mutation. Men with certain inherited BRCA gene mutations also face an increased risk of breast cancer. BRCA mutations may increase the risk of other types of cancer in women and men as well.
Once detected, and depending on the mutation, surveillance and surgical options are available for reducing the risk of cancer.
Who should consider BRCA gene testing?
You might be at increased risk of having a BRCA gene mutation — and a candidate for BRCA gene testing — if you have:
- A personal history of breast cancer diagnosed at a young age (premenopausal or younger than age 50)
- A personal history of triple negative breast cancer diagnosed at age 60 or younger
- A personal history of breast cancer affecting both breasts (bilateral breast cancer)
- A personal history of both breast and ovarian cancers
- A personal history of ovarian cancer
- A personal history of breast cancer and one or more relatives with breast cancer diagnosed at age 50 or younger, one relative with ovarian cancer, or two or more relatives with breast or pancreatic cancer
- A history of breast cancer at a young age in two or more close relatives, such as your parents, siblings or children
- A male relative with breast cancer
- A family member who has both breast and ovarian cancers
- A family member with bilateral breast cancer
- A relative with ovarian cancer
- A relative with a known BRCA1 or BRCA2 mutation
- Ashkenazi (Eastern European) Jewish ancestry, with a close relative who has breast, ovarian or pancreatic cancer at any age
Ideally, in a family that might carry a BRCA 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 taking the BRCA test. 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.
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 a BRCA gene 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.
Proceeding with genetic testing after you meet with a genetic counselor is up to you.
If you decide to proceed with the BRCA genetic test, 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. Your blood sample then goes 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 it 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 takes several 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. Federal and state laws help ensure the privacy of your genetic information and protect against discrimination in health insurance and employment.
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 that you'll ultimately 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.
Your options might include:
Increased screening (surveillance). Surveillance for breast cancer if you have a BRCA mutation means having clinical breast exams every six months and mammograms and magnetic resonance imaging (MRI) exams every year. Some experts recommend alternating mammogram and breast MRI every six months. These tests don't prevent breast cancer but may help detect it early. Substituting mammography plus MRI screening for prophylactic mastectomy can offer comparable survival.
You may also choose to perform monthly breast self-exams to become familiar with the normal texture of your breast tissue. Potentially worrisome breast changes may be easier for you to detect earlier if you know what's normal.
Surveillance for ovarian cancer with available tests has not been found to be effective in early detection of cancer, nor has it shown a survival benefit. The tests include having semiannual pelvic exams and yearly transvaginal ultrasound imaging and a blood test to measure your cancer antigen 125 level.
- Oral contraceptives. Oral contraceptive use has been shown to reduce ovarian cancer risk in BRCA mutation carriers. Your risk of breast cancer goes up slightly if you use oral contraceptives for more than five years, however.
Medication to reduce your risk of cancer (chemoprevention). Tamoxifen reduces the risk of developing breast cancer by about 50 percent in women who are at increased risk of the disease. Some small studies have shown that tamoxifen may help lower the risk in women specifically with a BRCA2 gene mutation.
Other preventive medications include raloxifene (Evista), exemestane (Aromasin) and anastrozole (Arimidex), which also help reduce the chance of breast cancer in postmenopausal women at high risk, though they haven't been studied specifically in women with BRCA mutations.
Preventive surgery. Preventive (prophylactic) mastectomy — surgical removal of healthy breast tissue — reduces breast cancer risk for BRCA gene carriers by about 90 percent, according to several studies. Removal of healthy fallopian tubes and ovaries (preventive salpingo-oophorectomy) reduces breast cancer risk by as much as 50 percent in premenopausal women, and it reduces ovarian cancer risk in both pre- and postmenopausal women.
Preventive surgery doesn't eliminate all cancer risk. It's possible for cancer to develop in any tissue that couldn't be removed through surgery.
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.
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.
Keep in mind that a negative test result doesn't eliminate the chance of developing a nonhereditary breast cancer. You still have the same cancer risk as that of the general population.
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.
Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this disease.
Jan. 25, 2019