All women thinking about taking medicine for breast cancer risk reduction should first have a health care professional assess their risk of developing breast cancer. There are tools that can be used to figure out breast cancer risk – see the “Breast cancer risk assessment” section.
The 2 big studies of these drugs, the Breast Cancer Prevention Trial (BCPT) and the Study of Tamoxifen and Raloxifene (STAR) looked only at women who had at least a 1.7% risk of developing breast cancer over the next 5 years. 1.7% is the risk of a healthy woman aged 60.
A woman younger than age 60 could have the same risk as a 60-year-old (or even higher) if she has one or more of these factors:
- A BRCA1 or BRCA2 gene mutation
- Has already had breast cancer
- Any past breast biopsy, especially one that shows either atypical ductal hyperplasia (ADH) or lobular carcinoma in situ (LCIS). These conditions are signs of an increased chance of developing invasive breast cancer.
- Several close relatives – mother, sister(s), daughter(s) with breast cancer – especially if they were diagnosed before menopause
- Never had any children, or had a first child after age 30
- Started menstrual periods before age 12 or went through menopause after age 55
To learn more about your own breast cancer risk and whether you might want to talk to your doctor about taking a drug to reduce your risk see the section called “Breast cancer risk assessment.”
Are there women who should NOT take one of these drugs to reduce their breast cancer risk?
Tamoxifen
Tamoxifen should not be used to reduce breast cancer risk in women who:
- Have ever had blood clots or who develop blood clots that need medical treatment
- Are taking medicines to thin their blood (for instance, warfarin, Coumadin®, heparin – drugs that keep blood from clotting)
- Have or have had high blood pressure, obesity, or diabetes; or current smokers (tamoxifen increases the risk of blood clots in these women)
- Are pregnant or planning to become pregnant
- Are breast-feeding
- Are younger than 35 years old
- Are younger than 60 years old and are not at increased risk
- Have not had any breast cancer risk assessment
- Are taking hormone replacement therapy, raloxifene, or an aromatase inhibitor
- Have been diagnosed with any type of uterine cancer
There may be other reasons that a woman should not take tamoxifen, such as cataracts or having been previously found to have atypical hyperplasia of the uterus.
Women should talk with their doctors about their total health picture in order to make the best possible choices.
Tamoxifen may cause birth defects if it is taken at the time of conception or during pregnancy. Women taking this drug need to use a barrier or another method of birth control that does not involve hormones. If you are pregnant, breast-feeding, or planning to have children tell your doctor before you start tamoxifen.
Do not take birth control pills (oral contraceptives) or other birth control that contains hormones while taking this drug without checking with your doctor first.
Raloxifene
Raloxifene should not be used to reduce breast cancer risk in women who:
- Have ever had blood clots or who develop blood clots that need medical treatment
- Are taking medicines to thin their blood (for instance, warfarin, Coumadin, heparin – drugs that keep blood from clotting)
- Have or have had high blood pressure, obesity, or diabetes; or current smokers (these are linked to an increased risk of blood clots)
- Are pre-menopausal (have not yet gone through menopause
- Are younger than 35 years old
- Are younger than 60 years old and are not at increased risk
- Have not had any breast cancer risk assessment unless they have osteoporosis
- Are taking hormone replacement therapy, tamoxifen, or an aromatase inhibitor
- Have been diagnosed with any type of uterine cancer (although the risk of uterine cancer is lower with raloxifene than with tamoxifen, it may not be zero)
There may be other reasons that a woman should not take raloxifene. Women with a history of heart disease who take raloxifene have an increased risk of stroke.
Women should talk with their doctors about their total health picture in order to make the best possible choices.
Raloxifene has not been studied for safety in pre-menopausal women, so it is only given to women who have gone through menopause. It may cause birth defects if it is taken at the time of conception or during pregnancy.
Should women who have an increased risk of breast cancer take one of these drugs?
Women with an increased risk of breast cancer should think about taking a medicine to reduce their risk. As with any medical procedure or treatment, the decision to take such a drug is a personal one in which the benefits and risks must be discussed with your doctor.
The balance of these benefits and risks vary depending on a woman’s risk of developing breast cancer, her personal health history, and how she and her doctor weigh the benefits and risks.
Even if a woman has an increased risk of breast cancer, a drug like tamoxifen or raloxifene may not be right for her. Any woman who is thinking about taking a drug to lower breast cancer risk should talk with her doctor about her personal health situation to make the best decision.
Should women who do NOT have an increased risk of breast cancer take one of these drugs?
The best studies of these drugs were in women with an increased risk of breast cancer. In those women, the benefits outweighed the risks.
In fact, tamoxifen has never been studied in healthy women at average risk for breast cancer, so there’s no way to know if it would lower their breast cancer risk and, if so, by how much. Only higher risk women were allowed to take part in studies to reduce risk because the overall benefit of taking a drug for breast cancer risk reduction is greatest in these women.
The FDA approved tamoxifen to be used for breast cancer risk reduction in women who are at high risk -- not in average-risk women.
Raloxifene was found to lower breast cancer risk in post-menopausal women with osteoporosis who did not have an increased risk of breast cancer, so it is an option for these women.
Women at average risk would have the same side effects and risks of the drug, but less benefit because fewer of these women would be likely to develop breast cancer. There is no recommendation to take any breast cancer chemoprevention if you are not thought to be at an increased risk. Women who are not at increased risk may wish to talk with their doctors about their specific situations.
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