Chemoprevention of Breast Cancer: A Summary of the Evidence for the U.S. Preventive Services Task Force

2 July 2002 | Volume 137 Issue 1 | Pages 59-69

Purpose: Chemoprevention offers promise as a strategy for reducing morbidity and mortality from breast cancer in women. This review examined the evidence for the effectiveness of chemoprevention in women without a history of breast cancer.

Data Sources: MEDLINE (1966 to December 2001).

Study Selection: English-language, randomized, controlled trials (RCTs) of chemoprevention of breast cancer in women without a previous diagnosis of breast cancer were examined, and 4 relevant trials, 3 involving tamoxifen and 1 involving raloxifene, were selected. Trials that provided data on the harms of tamoxifen or raloxifene, studies of the costs of chemoprevention, and studies of risk assessment were also reviewed.

Data Extraction: Four reviewers independently abstracted data on key variables, including study population, sample size, randomization, treatment, and outcomes.

Data Synthesis: The largest of the RCTs of tamoxifen reported a 49% reduction in relative risk (0.51 [95% CI, 0.39 to 0.66]) for invasive cancer among women with an estimated 5-year breast cancer risk of at least 1.66%. The other tamoxifen trials did not observe a statistically significant benefit, but only a few women in each trial took tamoxifen during the entire study period. The raloxifene study of postmenopausal women with osteoporosis found a 76% reduction in relative risk (0.24 [CI, 0.13 to 0.44]) for invasive breast cancer. Tamoxifen and raloxifene were effective only against estrogen receptor-positive tumors. Both drugs increased risk for venous thromboembolic disease and hot flashes; tamoxifen increased risk for endometrial cancer and stroke.

Conclusions: Tamoxifen and raloxifene reduce the incidence of estrogen receptor-positive breast cancer in women. The relative risk reduction seems similar across all breast cancer risk groups. The absolute risk reduction varies by risk factors for breast cancer, however, and must be balanced against the potential harms to judge the appropriateness of treatment for individual women.

Author and Article Information

From Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Virginia Commonwealth University, Fairfax, Virginia; American College of Physicians-American Society of Internal Medicine, Philadelphia, Pennsylvania; and Research Triangle Institute, Research Triangle Park, North Carolina.

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 U.S. Agency for Healthcare Research and Quality, the U.S. Department of Defense, or the U.S. Department of Health and Human Services.

Acknowledgments: The authors thank David Atkins, MD, MPH, Director; Dana Best, MD, MPH; and Eve Shapiro of the Agency for Healthcare Research and Quality Clinical Prevention Program. They thank Carmen Lewis, MD, MPH, and Margaret Wooddell, MA, for assistance in reviewing the studies of tamoxifen and raloxifene cited in this paper; Audrina J. Bunton, BA, and Lynn Whitener, MSLS, DrPH, of University of North Carolina, and Sonya Sutton, BSPH, and Loraine Monroe of the Research Triangle Institute; and Bahjat Qaqish, MD, PhD, for statistical assistance.

Grant Support: This study was developed by the Research Triangle Institute-University of North Carolina Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality (Contract No. 290-97-0011), Rockville, Maryland.

Requests for Reprints: Reprints are available from the AHRQ Web site at http://www.ahrq.gov (click on Preventive Services) and in print through the AHRQ Publications Clearinghouse (800-358-9295).

Current Author Addresses: Dr. Kinsinger: Program on Prevention, CB# 7508, Wing D, Room 383, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7508.

Dr. Harris: Cecil G. Sheps Center for Health Services Research, CB# 7590, University of North Carolina at Chapel Hill, 725 Airport Road, Chapel Hill, NC 27599-7590.

Dr. Woolf: Department of Family Practice, Virginia Commonwealth University, 3712 Charles Stewart Drive, Fairfax, VA 22033.

Dr. Sox: American College of Physicians-American Society of Internal Medicine, 190 N. Independence Mall West, Philadelphia, PA 19106-1572.

Dr. Lohr: Research Triangle Institute, 3040 Cornwallis Road, Research Triangle Park, NC 27709-2194.