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Chemoprevention of Breast Cancer

Systematic Evidence Reviews, No. 8

, MD, MPH, , MD, MPH, , MD, MPH, and , MA.

Research Triangle Institute, University of North Carolina Evidence-based Practice Center

Structured Abstract

Context:

Breast cancer is an important cause of morbidity and mortality among women in the United States. Secondary prevention by screening is only moderately effective. Primary prevention by chemoprevention may be an important strategy.

Objective:

To examine the evidence about the benefits and harms of breast cancer chemoprevention for pre- and postmenopausal women for the U.S. Preventive Services Task Force.

Data Sources:

We identified English-language articles on breast cancer chemoprevention from comprehensive searches of the MEDLINE database from 1966 through January 2000. We used systematic reviews, hand searching of relevant articles, and extensive peer review to identify important articles and assure completeness.

Study Selection:

We included all randomized controlled trials of chemoprevention agents of at least one year's duration among women at low to high risk for breast cancer that measured clinical endpoints of breast cancer incidence and harms of treatment. We also included, as background, other studies that reported benefits and harms of the chemopreventive agents.

Data Extraction:

We extracted the following data from the four included articles: demographic and breast cancer risk details about patients, inclusion criteria, study design and randomization, duration, interventions, and outcome measures. We evaluated the internal and external validity of each article. We judged the overall quality of evidence on aggregate internal and external validity and coherence of the results.

Data Synthesis:

Strong, direct evidence shows that tamoxifen reduces by approximately half the incidence of invasive and noninvasive breast cancer in pre- and postmenopausal women at high risk for breast cancer. Similarly, evidence from one study suggests that raloxifene reduces by the same amount the incidence of invasive breast cancer in postmenopausal women at low to average risk for breast cancer. Raloxifene also reduces the risk of vertebral fractures in postmenopausal women with osteoporosis. Both drugs are associated with an increased risk of venous thromboembolic disease (deep vein thrombosis and pulmonary embolism); tamoxifen is also associated with an increased risk of endometrial cancer. The balance between benefits and harms varies among subgroups of women, depending on age, predicted risk of breast cancer, and hysterectomy status.

Conclusions:

Tamoxifen and raloxifene reduce the incidence of breast cancer in women over a wide range of ages and levels of breast cancer risk. Both drugs may also have other benefits, but they may cause harm in otherwise healthy women who take them for prophylaxis.

Contents

6010 Executive Boulevard, Suite 300 Rockville, Maryland 20852.

3040 Cornwallis Road P.O. Box 12194 Research Triangle Park, North Carolina 27709.

Submitted to: Agency for Healthcare Research and Quality.1 Contract No. 290-97-0011 Task No. 3. Submitted by: Research Triangle Institute, University of North Carolina Evidence-based Practice Center .2

1

6010 Executive Boulevard, Suite 300 Rockville, Maryland 20852.

2

3040 Cornwallis Road P.O. Box 12194 Research Triangle Park, North Carolina 27709.

Bookshelf ID: NBK42584PMID: 20722177
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