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Breast Cancer Screening: A Summary of the Evidence for the U.S. Preventive Services Task Force
- Linda L. Humphrey, MD, MPH;
- Mark Helfand, MD, MS;
- Benjamin K.S. Chan, MS; and
- Steven H. Woolf, MD, MPH
- From Oregon Health & Science University and Portland Veterans Affairs Medical Center, Portland, Oregon; and Medical College of Virginia, Virginia Commonwealth University, Fairfax, Virginia.
Abstract
Purpose: To synthesize new data on breast cancer screening for the U.S. Preventive Services Task Force.
Data Sources: MEDLINE; the Cochrane Controlled Trials Registry; and reference lists of reviews, editorials, and original studies.
Study Selection: Eight randomized, controlled trials of mammography and 2 trials evaluating breast self-examination were included. One hundred fifty-four publications of the results of these trials, as well as selected articles about the test characteristics and harms associated with screening, were examined.
Data Extraction: Predefined criteria were used to assess the quality of each study. Meta-analyses using a Bayesian random-effects model were conducted to provide summary relative risk estimates and credible intervals (CrIs) for the effectiveness of screening with mammography in reducing death from breast cancer.
Data Synthesis: For studies of fair quality or better, the summary relative risk was 0.84 (95% CrI, 0.77 to 0.91) and the number needed to screen to prevent one death from breast cancer after approximately 14 years of observation was 1224 (CrI, 665 to 2564). Among women younger than 50 years of age, the summary relative risk associated with mammography was 0.85 (CrI, 0.73 to 0.99) and the number needed to screen to prevent one death from breast cancer after 14 years of observation was 1792 (CrI, 764 to 10 540). For clinical breast examination and breast self-examination, evidence from randomized trials is inconclusive.
Conclusions: In the randomized, controlled trials, mammography reduced breast cancer mortality rates among women 40 to 74 years of age. Greater absolute risk reduction was seen among older women. Because these results incorporate several rounds of screening, the actual number of mammograms needed to prevent one death from breast cancer is higher. In addition, each screening has associated risks and costs.
Article and Author Information
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Note: This manuscript is based on a longer systematic evidence review that was reviewed by outside experts and representatives of professional societies. A complete list of peer reviewers is available online at http://www.ahrq.gov/clinic/uspstfix.htm.
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Disclaimer: The authors of this article are responsible for its contents, including any clinical or treatment recommendations. No statement in this article should be construed as an official position of the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.
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Acknowledgments: The authors thank Stephanie Detlefsen, MD, for her contribution to this evidence review and David Atkins, MD, MPH, from the Agency for Healthcare Research and Quality and members of the U.S. Preventive Services Task Force for their comments on earlier versions of this review. They also thank Kathryn Pyle Krages, AMLS, MA, Susan Carson, MPH, Patty Davies, MS, Susan Wingenfeld, and Jim Wallace for their help with preparation of the manuscript and the full systematic evidence review.
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Grant Support: This study was conducted by the Oregon Health & Science University Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality (contract no. 290-97-0018, task order no. 2), Rockville, Maryland.
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Requests for Single Reprints: Reprints are available from the Agency for Healthcare Research and Quality Web site (http://www.preventiveservices.ahrq.gov) or the Agency for Healthcare Research and Quality Publications Clearinghouse (800-358-9295).
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Current Author Addresses: Drs. Humphrey and Helfand and Mr. Chan: Oregon Health & Science University, Mailcode BICC, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098.
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Dr. Woolf: Virginia Commonwealth University, 3712 Charles Stewart Drive, Fairfax, VA 22033.
- Copyright ©2004 by the American College of Physicians
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