If you test positive for a BRCA1 or BRCA2 mutation, and you have never had breast cancer, you now know that you are at much higher-than-average risk of developing it over the course of your lifetime. For women, the risk of getting breast cancer in your lifetime if you have a BRCA1 or BRCA2 abnormality is between about 40% and 85% — about 3 to 7 times greater than that of a woman who does not have the mutation. Your lifetime risk of ovarian cancer is significantly elevated as well: 16% to 60%, versus just under 2% for the general population. Men with BRCA abnormalities are considered to have a higher lifetime risk of male breast cancer, especially if the BRCA2 gene is affected. One study found that men with a BRCA2 mutation have a 7% lifetime risk of developing breast cancer. They also may be at increased risk of developing prostate cancer.
Whether you are a man or a woman, an abnormal genetic test result means there is a 50% chance you could have passed the BRCA1 or BRCA2 mutation on to your children.
Researchers have been working to build their understanding of how breast cancers in women with BRCA mutations may differ from other breast cancers. Some of their findings include:
- Breast cancers in women with BRCA1 abnormalities are more likely to be estrogen-receptor-negative — meaning that the cancer’s growth is not fueled by the hormone estrogen — and to have “high-grade” cell growth. Both of these characteristics mean that chemotherapy will be more effective than hormonal (anti-estrogen) therapy in treating these cancers.
- BRCA1- and BRCA2-related cancers often test negative for overexpression of the gene known as HER2/neu. This genetic abnormality is not inherited, as BRCA1 and BRCA2 mutations are, but can develop in women over time. When the HER2 gene is overexpressed, the cancer cells have too many HER2 receptors (human epidermal growth factor receptor). HER2 receptors receive signals that stimulate the growth of breast cancer cells. HER2-positive breast cancer is considered to be a more aggressive form of the disease, but it can be treated with Herceptin (chemical name: trastuzumab), a medication that targets HER2. Most BRCA1- and BRCA2-related cancers cannot be treated with Herceptin because they are HER2-negative.
- Women with BRCA1 or BRCA2 gene abnormalities have no greater risk than other women of having multiple cancers in the same breast when their breast cancer is diagnosed.
- A 2005 study suggested that women with DCIS (ductal carcinoma in situ) are just as likely to have inherited gene abnormalities as those with invasive breast cancer.
If you have breast cancer
If you have a breast cancer gene abnormality and you develop breast cancer, your doctor will work with you to determine how your BRCA status might affect your treatment decisions. For example, if you have a BRCA1 mutation, the breast cancer is less likely to be estrogen receptor-positive, which means that you may not be a candidate for treatment with hormonal therapy. If you have a BRCA2 mutation, however, you are more likely to be a candidate for hormonal therapy.
You’ll also want to talk with your doctor about reducing the risk of a new, second breast cancer or ovarian cancer. Women with breast cancer and a BRCA1 or BRCA2 abnormality have a significantly greater risk of developing a new, second breast cancer, as well as ovarian cancer.
If you want to lower your risk of a future breast cancer or ovarian cancer
Whether or not you’ve ever had breast cancer, knowing that you have a BRCA mutation means that you are at much greater risk of developing breast and possibly ovarian cancer in the future. The latest research offers these insights about strategies for lowering those risks:
- Preventive or "prophylactic" mastectomy, or removal of both breasts, has been found to reduce the risk of breast cancer in high-risk women by about 90%. After a diagnosis of one breast cancer in a woman with a genetic abnormality, the risk of her getting a new breast cancer is approximately 3% every year (for example, 15% over 5 years). Without BRCA1 or BRCA2, the risk of developing a new breast cancer after one episode of breast cancer is only 1% per year.
Preventive or prophylactic oophorectomy, or removal of both ovaries, can reduce breast cancer risk when it is done before menopause, because it takes away the body’s main source of the hormone estrogen. It also can greatly reduce ovarian cancer risk. However, a 2008 study involving more than 1,000 women with BRCA mutations showed that the benefits of ovary removal may be different depending on the type of mutation:
- BRCA1 carriers: Ovary removal reduced ovarian cancer risk in BRCA1 carriers by 85%, but it did not significantly reduce their breast cancer risk. Women with BRCA1 mutations are more likely to develop breast cancers that are not fueled by the hormone estrogen (estrogen-receptor-negative breast cancer). So removing the ovaries, the body’s main source of estrogen, did not provide significant benefit in terms of breast cancer risk.
- BRCA2 carriers: Women with a BRCA2 mutation had a 72% decrease in their risk of breast cancer after ovary removal. That’s because breast cancer in BRCA2 carriers is more likely to be estrogen-receptor-positive. The study did not find a significant reduction in ovarian cancer risk for these women. BRCA2 mutations have not been found to play as important a role in ovarian cancer risk as BRCA1 mutations do.
- Tamoxifen is a hormonal therapy that blocks the effects of estrogen on breast tissue. In the late 1990s, a clinical trial called the Breast Cancer Prevention Trial first found that tamoxifen reduced breast cancer risk by 45% to 50% in women considered to be at high risk for breast cancer. However, later results revealed that the risk-reduction benefit of tamoxifen appears to be greatest for women with BRCA2 mutations, who tend to develop breast cancers that are fueled by the hormone estrogen. The trial found that in women 35 years of age or older who had not been diagnosed with breast cancer and who took tamoxifen, those who were BRCA2-positive had a 62% reduction in breast cancer risk, while those who were BRCA1-positive did not have a significant reduction in breast cancer risk. It’s not clear whether tamoxifen treatment lowers breast cancer risk in BRCA1-positive women younger than 35 who've never been diagnosed with breast cancer. Other research has shown that both BRCA1-positive and BRCA2-positive women previously diagnosed with breast cancer in one breast can lower their risk of developing a new breast cancer in the opposite breast by taking tamoxifen.
If you want to try to increase the odds of early detection
Another option besides preventive surgery is to undergo more frequent cancer screenings in an effort to catch cancer early, should it ever develop. Although more frequent screenings do not guarantee early detection of cancer, they are generally recommended for women who do not wish to have preventive surgery.
You can work with your doctor to come up with a screening schedule that is right for you. For example, you might take the following steps:
- Begin annual mammograms at age 25, or 10 years before the earliest age at which a family member was diagnosed — whichever comes first. Digital mammography may provide added benefit. MRI (magnetic resonance imaging) of the breasts performed by experienced centers can also be very useful. Consider participating in a clinical trial evaluating newer methods of early detection.
- If you have a family history of ovarian cancer, begin annual screening at age 25, including pelvic exams by a gynecologist, annual pelvic ultrasound with an intravaginal probe, and blood tests for a special protein called CA-125. Consider participating in a clinical trial evaluating newer methods of early detection.
- Have a clinical breast exam every 6 months, and examine your breasts monthly.
- Consider participating in a clinical trial of cancer prevention strategies.