- Medicines to Reduce Breast Cancer Risk
- Tamoxifen and raloxifene
- What are the risks in taking these drugs?
- How long should women take these drugs to lower breast cancer risk?
- Do these drugs have the same risks as post-menopausal hormone therapy?
- Who should consider taking a drug to reduce their breast cancer risk?
- Breast cancer risk assessment
- Weighing risks versus benefits
- Aromatase inhibitors
- Other compounds being studied
- What does all of this mean for you?
- To learn more
Weighing risks versus benefits
Based largely on the results of the Breast Cancer Prevention Trial (BCPT), the Food and Drug Administration (FDA) approved tamoxifen to reduce the risk of breast cancer in women whose risk of developing the disease was at least 1.7% within the next 5 years based on their Gail score (calculated using the Gail Model risk tool). This included all women over the age of 60, as well as those between 35 and 59 with factors that increased their risk to this level, whether or not they had gone through menopause.
Based largely on the results of the Study of Tamoxifen and Raloxifene (STAR), the FDA approved raloxifene to reduce the risk of breast cancer in post-menopausal women whose risk of developing the disease was at least 1.7% within the next 5 years based on the Gail score (calculated using the Gail Model risk tool). This drug is also approved to lower breast cancer risk in post-menopausal women with osteoporosis who have an average risk of breast cancer.
Still, having a 1.7% risk of developing breast cancer over 5 years is the same as having a 98.3% chance of NOT getting breast cancer in the next 5 years. This means that most of the women who take a drug to lower breast cancer risk would never have developed cancer in the first place. Also, because these drugs can have some serious side effects, not everyone who meets the FDA requirements for taking tamoxifen or raloxifene for breast cancer risk reduction would necessarily have an overall benefit from it.
Since these studies came out, researchers have tried to look at more than just a woman’s risk of developing breast cancer when trying to decide whether she might benefit. For example, older women are at higher risk of breast cancer than younger women are, which could mean one of these drugs might be more likely to reduce this particular risk. But older women are also more likely to have a stroke or blood clot, which could make the drugs riskier for them.
Pre-menopausal women with a risk of developing breast cancer that is greater than 1.7% in 5 years are likely to have an overall benefit from taking tamoxifen to reduce their risk. (Raloxifene is not an option in these women because it’s not approved for women who haven’t gone through menopause.)
Most post-menopausal women are likely to have an overall benefit from taking tamoxifen. The benefits will most likely outweigh the risks in groups of women who are not obese or who have had a hysterectomy. Most post-menopausal women are also likely to benefit from taking raloxifene. Though the benefits are not as high, the risks are lower.
Studies estimate that about 3 out of 20 (15%) women over the age of 35 would be eligible to take tamoxifen to reduce their risk of breast cancer, according to the FDA criteria. (Because most of these women are pre-menopausal, few of them would be eligible to take raloxifene.) But only about 1 in 3 of these eligible women would have benefits that would be likely to outweigh the risk.
Generally speaking, younger women at high risk of breast cancer appear to have a better benefit-to-risk ratio from tamoxifen than do older women. As with any drug, it’s important to remember that each woman is unique, and the possible benefits and risks for her depend on many factors.
A final word on taking tamoxifen or raloxifene to reduce breast cancer risk
Scientists are working very hard to develop information about competing risks, such as how a woman’s risk of heart disease or uterus cancer should affect her decisions about breast cancer risk reduction. As new information comes in, recommendations about who should and who should not take these drugs may change.
Also keep in mind that your risk changes over time with age, with a new diagnosis of breast cancer in your family, or if you have a breast biopsy.
Some experts think that more research is needed to learn more about the benefits and risks of taking these drugs for breast cancer risk reduction. Although studies have shown a lower risk of breast cancer, this did not translate into any effect on deaths from breast cancer or other causes in women followed for up to 10 years.
More research may be needed to answer the many questions about using one of these drugs to reduce the risk of breast cancer.
Last Medical Review: 06/04/2013
Last Revised: 07/17/2013