Tamoxifen Also Effective in Stopping Abnormal Breast Cells from Becoming Cancerous

University of Pennsylvania Cancer Center
Last Modified: May 18, 1999

Last year a major study of 13,000 women demonstrated that tamoxifen can significantly reduce the risk of developing breast cancer in some women. In October 1998, the federal Food and Drug Administration (FDA) approved the drug for use in women at increase risk of developing the disease. Now, after further analysis of the data, researchers have found that the drug also benefits women who have benign conditions that may or may not develop into invasive breast cancer.

Dr. Donald Wickerham and his colleagues at the National Surgical Adjuvant Breast and Bowel Project (NSABP) studied a sub-set of 2,019 women in the original Breast Cancer Prevention Trial, which enrolled more than 13,000 participants. They specifically looked at women whose biopsied breast tissue showed either lobular carcinoma in-situ (LCIS) or atypical hyperplasia (AH). These relatively rare conditions are considered indicators that a woman is at risk or developing the disease.

Wickerham found that women with LCIS or AH who took tamoxifen significantly reduced their chance of developing invasive breast cancer compared with a control group that took a placebo, or dummy pill. In the study, 8 women with LCIS in the tamoxifen group developed cancer, compared to 18 women who took a placebo — a 66 percent reduction. Results were even more dramatic for women diagnosed with AH. Only 3 women with AH who took tamoxifen developed invasive breast cancer compared to 23 women in the control group — an 86 percent reduction in invasive breast cancer cases.