Evidence Summary

What is an Evidence Summary?

Key messages from scientific research that's ready to be acted on

Got It, Hide this
  • Rating:

Tamoxifen 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?


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.


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


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.


Neither reduced cancer-specific or all-cause mortality rates.


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).


Tamoxifen increased incidence more than raloxifene and placebo.



A harmless, inactive, and simulated treatment.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

Related Web Resources

  • Colorectal cancer test recommendations

    Health Link B.C.
    Colorectal testing every 1-2 years is recommended for people between ages 50 and 74. Your doctor may recommend screening before age 50 and more often if you have an increased risk of this type of cancer (eg. family history of colon cancer, polyps or Crohn's disease).
  • Breast cancer Screening video

    Canadian Task Force on Preventive Health Care
    Women ages 50-74 should have a mammogram every 2 to 3 years, if they are not at high risk of breast cancer. Discuss with your doctor whether you should have a mammogram if you are over age 75.
  • Dance therapy for people with cancer

    Evidently Cochrane
    Dance therapy does not appear to have a large benefit on improving physical or psychological symptoms of people with cancer, such as depression, fatigue or body image. However, you should dance if it helps you feel better.
DISCLAIMER These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (info@mcmasteroptimalaging.org).

Register for free access to all Professional content

Want the latest in aging research? Sign up for our email alerts.

Support for the Portal is largely provided by the Labarge Optimal Aging Initiative. AGE-WELL is a contributing partner. Help us to continue to provide direct and easy access to evidence-based information on health and social conditions to help you stay healthy, active and engaged as you grow older. Donate Today.

© 2012 - 2019 McMaster University | 1280 Main Street West | Hamilton, Ontario L8S4L8 | +1 905-525-9140 | Terms Of Use