Despite the importance of screening mammography and breast examination in breast cancer control, randomized trials show modest effect of screening on breast cancer deaths, according to background information in the article. A national breast cancer prevention trial showed a 49 percent reduction in breast cancer incidence in high-risk individuals who received tamoxifen. However, according to the article, the same study also showed that the drug increased the risk of endometrial (uterus) cancer, pulmonary embolism (sudden blockage of an artery in the lung), blood clots in the deep veins, and stroke.
Carmen L. Lewis, M.D., M.P.H., from The University of North Carolina at Chapel Hill, and colleagues surveyed 605 women aged 40 to 69 years in ten general internal medicine practices in North Carolina in 2000. The survey was designed to determine each woman's breast cancer risk and then to assess eligibility for chemoprevention (using tamoxifen to prevent breast cancer). The researchers determined the women's five-year breast cancer risk based on age, ethnicity, number of first-degree relatives with breast cancer, age at first menstruation, age at first live birth, number of breast biopsies, and presence of atypical hyperplasia (abnormal cells that may be indicative of cancer) in a biopsy specimen. Women with an estimated five-year breast cancer risk of at least 1.66 percent were defined as having an increased breast cancer risk. To determine the possible risks of taking tamoxifen, the women were questioned about their medical history; specifically, whether their physicians had told them they had high blood pressure, diabetes mellitus, blood clots in the legs, or blood clots in the lungs.
The researchers found that among white women, nine percent in their 40s, 24 percent in their 50s, and 53.4 percent in their 60s had a five-year estimated breast cancer risk of 1.66 percent or greater. Among black women, 2.9 percent in their 40s, 7.1 percent in their 50s, and 13 percent in their 60s had a similar risk. When the possible side effects of tamoxifen were considered in white women, ten percent or fewer in all age groups were judged to be potentially appropriate for chemoprevention using tamoxifen. In women identified as at an increased risk for breast cancer, the maximum proportion of breast cancers that would be prevented was 6 to 8.3 percent, according to the researchers' calculations.
The authors write: "Small numbers of women in primary care practices are eligible for discussions about chemoprevention; the maximum proportion of breast cancers prevented is also small. Challenges lie in targeting discussions to the most appropriate women and in finding new chemoprevention strategies that have less risk of harms."
(Arch Intern Med. 2004; 164: 1897 – 1903. Available post-embargo at www.archinternmed.com)
Editor's note: This study was supported by a grant from the National Cancer Institute, Bethesda, Md., and The University of North Carolina at Chapel Hill Lineberger Comprehensive Cancer Center, and by a grant from the Agency for Healthcare Research and Quality, Rockville, Md. Dr. Lewis is the recipient of a Cancer Control Career Development Award for Primary Care Physicians from the American Cancer Society, Atlanta, Ga.
To contact Carmen L. Lewis, M.D., M.P.H., call David Williamson at 919-962-8596.
For more information, contact JAMA/Archives Media Relations at 312-464-JAMA (5262) or e-mail mediarelations@jama-archives.org.
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Archives of Internal Medicine