About the Medicines
Two different medicines can reduce the risk of breast cancer for women who have never had breast cancer before.
- Raloxifene (ra-LOX-ih-feen). It is only approved for use after menopause.
- Tamoxifen (ta-MOX-ih-fen). It is approved for use before and after menopause.
To reduce the risk of breast cancer, tamoxifen or raloxifene must be taken once every day for up to 5 years.
How They Work
Estrogen is a natural hormone found in the body. Some breast cancers use estrogen to grow. There is a place on some breast cancer cells, called a receptor, where estrogen can attach. This type of breast cancer is called estrogen-receptor positive cancer.
Tamoxifen and raloxifene work by blocking estrogen. They attach to the receptor, so estrogen can’t. Without estrogen, this type of breast cancer cell can’t multiply and grow.
Some breast cancers do not have estrogen receptors. This type of breast cancer is called estrogen-receptor negative cancer. It is not as common, but it is harder to treat.
- Raloxifene and tamoxifen reduce the risk of breast cancers that have estrogen receptors.
- They do not reduce the risk of breast cancers without estrogen receptors.
Possible Benefits
For women who have never had breast cancer, both tamoxifen and raloxifene reduce invasive breast cancer risk by about 50 percent.
Raloxifene does not lower the risk of non-invasive breast cancers (LCIS and DCIS). Research can’t tell us yet about tamoxifen and non-invasive breast cancers.
Possible Problems
Both tamoxifen and raloxifene have common side effects. They both can cause hot flashes. Tamoxifen can cause vaginal symptoms, like itching, dryness, or discharge. Raloxifene can cause leg cramps.
Some women who have taken tamoxifen or raloxifene have had a stroke. Research studies have found that the number of strokes in women taking these medicines is about the same as in women not taking these medicines. Talk with your doctor or nurse about your risk for stroke.
Other serious and life-threatening side effects can also happen.
- Blood clots in the lungs and legs. Tamoxifen and raloxifene raise the risk of blood clots. Blood clots happen more often with tamoxifen than raloxifene.
- Endometrial cancer (cancer of the uterus lining). Tamoxifen raises the risk of endometrial cancer. Raloxifene does not.
For every 100 women who take tamoxifen or raloxifene for 5 years, the medicine will cause a blood clot or endometrial cancer in about 1 woman.
Taking raloxifene or tamoxifen reduces a woman’s risk of some kinds of breast cancer. Some women who take these medicines will still get breast cancer.
Taking the medicines does not reduce the risk of dying from breast cancer. It also does not mean a woman will live longer. It is not clear why this is the case. Maybe the medicines reduce the kinds of breast cancers that are easiest to treat.
Thinking About the Decision
Most women will never get breast cancer. But some women are at higher risk than others. Talk with your doctor or nurse about your risk of breast cancer.
Tamoxifen and raloxifene can lower the risk of getting some kinds of breast cancer. These medicines also can raise the risk of serious problems. Talk with your doctor or nurse about your risk for serious problems from these medicines.
Think about these questions.
Do I have a high or a low risk for breast cancer? Do I have a high or low risk for serious problems from the medicine?
The risk of side effects should not be higher than the benefit of the medicine.
Can I stick with it?
These medicines need to be taken every day for up to 5 years. They often can cause hot flashes.
Does the cost of the medicines affect my decision?
The cost of the medicines may be important to you. They need to be taken for a long time, and the cost can add up. Check to see if your insurance covers using these medicines to lower breast cancer risk.