Some women are known to be at high risk for breast cancer. This includes women with a personal or family history of breast cancer and those who have had a precancerous condition called lobular carcinoma in situ (LCIS). Doctors have found that some medications may help lower their risk.
These drugs are called selective estrogen receptor modulators, or SERMs. Estrogen stimulates the growth of breast cells and can promote the growth of certain breast tumors. SERMs block the action of estrogen in the breast tissue by binding to the estrogen receptors in breast cells.
The U.S. Food and Drug Administration has approved two SERM medications to prevent breast cancer:
- Tamoxifen (Nolvadex) can be used by women age 35 and older who are at high risk for breast cancer. It is also used to treat breast cancer.
- Raloxifene (Evista) can be used by postmenopausal women at high risk for breast cancer. It has not been tested in women before menopause.
The STAR clinical trial was one of the largest breast cancer prevention studies ever done. Results from STAR found that both tamoxifen and raloxifene cut the risk of invasive breast cancer by about half in postmenopausal women at high risk for breast cancer. Tamoxifen also lowers the risk of LCIS and ductal carcinoma in situ (DCIS), which can lead to invasive breast cancer.
These medications also help reduce the risk of osteoporosis and fractures in postmenopausal women.
What are the risks?
SERMs can cause bothersome side effects similar to menopause symptoms, such as:
- Hot flashes
- Vaginal dryness
- Bladder control problems
- Leg cramps
- Pain during intercourse
- Joint pain
Serious problems are rare, but both tamoxifen and raloxifene are known to increase the risk of blood clots. Blood clots can lead to pulmonary embolism, deep vein thrombosis, or stroke. Tamoxifen is also linked to an increased risk of:
- Uterine cancer
Women who are pregnant should not take these medications. They could harm the fetus.
How can I decide about taking these medications?
The decision to take medications to reduce breast cancer risk is a personal one, and it can be a hard choice. You will need to weigh the risks of the treatment against the benefit of reducing your risk.
To decide if these medications are right for you:
- Talk to your doctor and a genetic counselor so you can get a better idea of your personal risk of breast cancer. Women sometimes think their risk is greater than it really is. A doctor can also help you understand the pros and cons of the medications.
- Consider your feelings. Some high-risk women are willing to risk the serious side effects associated with these medications to lower the risk of breast cancer. Others do not want to trade one risk for another.
- Discuss the decision with your loved ones. Hearing what your family and friends have to say may help you decide. In the end, though, it's your decision.
It's important to remember that taking the medications is not a guarantee that you won't get breast cancer. It only lowers the risk. And being at high risk for breast cancer doesn't mean you will get breast cancer.
Are there other choices?
There are two other known ways to lower breast cancer risk in women at high risk. You could:
- Have your breasts removed. A mastectomy is surgery to remove nearly all of the breast tissue, where breast cancer grows. This doesn't guarantee that you won't get breast cancer. But experts estimate that this surgery cuts the risk by about 90 percent.
- Have your ovaries removed. This lowers the risk of both breast cancer and ovarian cancer. Women with BRCA gene changes are at high risk for both types of cancer. But this surgery means you can't get pregnant, and it would put you into menopause. It might be a good choice if you are through having children and are near menopause anyway.
You could also watch and wait. Talk with your doctor if you are at high risk to decide how often you need mammograms, when you should start having them, and whether you should have other breast imaging studies. Mammograms and other breast imaging studies may find breast cancer early, when there's the best chance of a cure. This helps some women feel more comfortable with their risk.
Created on 10/18/1999
Updated on 07/18/2011
- National Cancer Institute. Study of Tamoxifen and Raloxifene (STAR) trial.
- National Cancer Institute. Understanding cancer series: estrogen receptors/SERMs.
- U.S. Preventive Services Task Force. Chemoprevention of breast cancer.