Evidence Summary
What is an Evidence Summary?
Key messages from scientific research that's ready to be acted on
Got It, Hide thisTamoxifen and raloxifene each reduce invasive breast cancer; neither reduces mortality rates in the particular group
Nelson H, Smith B, Griffin J, et al. Use of medications to reduce risk for primary breast cancer: a systematic review for the U.S. Preventive Services Task Force. Ann Intern Med. 2013.158:604-14.
Review question
What is the current evidence on medications to reduce the risk for primary breast cancer?
Background
One U.S. health group has recommended medications to reduce the risk for primary breast cancer in women at an increased risk.
Studies show the effectiveness of several medications for breast cancer. Tamoxifen and raloxifene are the only approved medications for this purpose. And raloxifene is approved for post-menopausal women only. Their use is low.
It is not clear how to select patients for these medications. In addition to benefits, they may cause adverse health effects.
How the review was done
This summary is based on a systematic review of 7 randomized controlled trials (or RCTs) of the drugs tamoxifen or raloxifene in women who do not have breast cancer.
The studies compared tamoxifen with raloxifene, tamoxifen with placebo, and raloxifene with placebo.
The review looked at the effectiveness and the adverse effects. It also considered patient use of such medications and methods for identifying women at increased risk for breast cancer.
The U.S. Agency for Healthcare Research and Quality funded this research.
What the researchers found
Tamoxifen and raloxifene reduced the incidence of invasive breast cancer by 7 to 9 cases in 1,000 women over 5 years compared with placebo.
New results from the Study of Tamoxifen and Raloxifene showed that tamoxifen reduced breast cancer incidence more than raloxifene by 5 cases in 1,000.
Neither medication reduced significantly noninvasive cancer incidence or mortality rates.
Both tamoxifen and raloxifene reduced the incidence of fractures. Tamoxifen increased the incidence of cataracts more than raloxifene and placebo.
Conclusions
Tamoxifen and raloxifene reduce the incidence of invasive breast cancer and fractures. They also increase the incidence of clot formation.
Results comparing tamoxifen and raloxifene
| Conditions | Tamoxifen and raloxifene |
| Invasive breast cancer | Both reduced incidence by 7 to 9 cases in 1,000 women over 5 years. |
| Relative effectiveness | Tamoxifen had greater effect on cancer incidence than raloxifene. |
| Mortality | Neither reduced cancer-specific or all-cause mortality rates. |
| Fractures | Both reduced incidence of fractures. |
| Clot formation | Tamoxifen increased incidence more than raloxifene by 4 cases in 1,000. |
| Uterus lining cancer | Tamoxifen increased incidence more than raloxifene and placebo (4 cases in 1,000). |
| Cataracts | Tamoxifen increased incidence more than raloxifene and placebo. |
Related Topics
Glossary
A harmless, inactive, and simulated treatment.
Studies where people are assigned to one of the treatments purely by chance.
A comprehensive evaluation of the available research evidence on a particular topic.
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