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Expert groups suggest that clinicians discuss use of tamoxifen to prevent breast cancer with women most likely to benefit from the drug. Only a few women visiting primary care doctors are potentially eligible for tamoxifen treatment, that is, they are at high risk of breast cancer but have a low risk of problems from tamoxifen, according to a recent study. Tamoxifen is a selective estrogen receptor modulator that has been shown to reduce the incidence of breast cancer. However, it has also been shown to increase the risk of endometrial cancer, blood clots, and stroke, particularly in women older than age 50.
Researchers at the RTI-University of North Carolina Evidence-based Practice Center, which is supported by the Agency for Healthcare Research and Quality (contract 290-97-0011), examined responses of 605 women (40 to 69 years of age) to questionnaires they completed in the waiting rooms of 10 general internal medicine practices in North Carolina in 2001. The researchers used a model of breast cancer risk to determine the proportion of women who were potentially eligible for tamoxifen chemoprevention and the proportion of breast cancers that could be prevented.
Estimated breast cancer risks were higher for white women in all age groups compared with black women in the same age group. Among white women, 9 percent of women in their 40s, 24 percent of women in their 50s, and 53 percent of women in their 60s had a 5-year estimated breast cancer risk of 1.66 percent or greater (considered high risk). Among black women, 3 percent in their 40s, 7 percent in their 50s, and 13 percent in their 60s had a similar risk. When adverse events from tamoxifen were considered in white women, 10 percent or fewer were potentially eligible to take the drug. If all of these women adhered to tamoxifen use for 5 years, a maximum of 6.0-8.3 percent of invasive cancers would be prevented over the next 5 years.
See "Breast cancer risk in primary care: Implications for chemoprevention," by Carmen I. Lewis, M.D., M.P.H., Linda S. Kinsinger, M.D., M.P.H., Russell P. Harris, M.D., M.P.H., and Robert J. Schwartz, M.A., in the September 27, 2004, Archives of Internal Medicine 164, pp. 1897-1903.
Editor's Note: Another AHRQ-supported study on a related topic found that women who received the breast cancer treatment they preferred had a better body image 2 years after treatment than women who did not, underscoring the importance of involving women in breast cancer treatment decisions. For more details, see Figueiredo, M.I., Cullen, J., Hwang, Y.T., and others (2004, October). "Breast cancer treatment in older women: Does getting what you want improve your long-term body image and mental health?" (AHRQ grant HS08395). Journal of Clinical Oncology 22(19), pp. 4002-4009.
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