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The Breast Cancer Prevention Trial (BCPT) is a clinical trial (a research study conducted with people) designed to see whether taking the drug tamoxifen (Nolvadex-R) can prevent breast cancer in women who are at an increased risk of developing the disease. The BCPT is also looking at whether taking tamoxifen decreases the number of heart attacks and reduces the number of bone fractures in these women. The study began recruiting participants in April 1992 and closed enrollment in September 1997; 13,388 women ages 35 and older are enrolled. Researchers with the National Surgical Adjuvant Breast and Bowel Project (NSABP) are conducting the study in more than 300 centers across the United States and Canada. The study is funded by the National Cancer Institute (NCI), the United States' primary agency for cancer research.
Tamoxifen is a drug, taken by mouth as a pill. It has been used for 25 years to treat patients with advanced breast cancer. Since 1985 it has also been recommended in the United States for adjuvant, or additional, therapy following surgery and/or radiation for early stage breast cancer. Tamoxifen works against breast cancer, in part, by interfering with the activity of estrogen, a female hormone that promotes the growth of breast cancer cells. For this reason, tamoxifen is often called an "anti-estrogen." In treatment, the drug slows or stops the growth of these cancer cells.
Research has shown that taking tamoxifen as adjuvant therapy for breast cancer not only helps prevent the original breast cancer from returning but also helps to prevent the development of new cancers in the opposite breast. Researchers believed that tamoxifen might have a similar beneficial effect for women at increased risk of breast cancer. While tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other body systems. Tamoxifen's estrogen-like effects include the lowering of blood cholesterol and the slowing of bone loss (osteoporosis).
At this point (data to January 31, 1998), women on the trial have been followed on the study for about 4 years. Results show 45 percent fewer diagnoses of invasive breast cancer in women who were randomized to take tamoxifen compared with women who were randomized to take the placebo (85 cases in the tamoxifen group versus 154 cases in the placebo group). Women on tamoxifen also had fewer diagnoses of noninvasive breast cancer, such as ductal carcinoma in situ (31 cases in the tamoxifen group versus 59 cases in the placebo group). Eight women have died of breast cancer, three women in the tamoxifen group and five women in the placebo group.
Women in the tamoxifen group had fewer bone fractures of the hip, wrist, and spine than women in the placebo group (47 cases in the tamoxifen group versus 71 cases in the placebo group). There was no difference in the number of heart attacks between the two groups.
Tamoxifen did increase the women's chances of three rare but serious health problems: endometrial cancer (cancer of the lining of the uterus), 33 cases in the tamoxifen group versus 14 cases in the placebo group; pulmonary embolism (blood clot in the lung), 17 cases in the tamoxifen group versus 6 cases in the placebo group; and deep vein thrombosis (blood clots in major veins), 30 cases in the tamoxifen group versus 19 cases in the placebo group.
For more information on this study, see the National Cancer
Institutes Cancer Facts-Prevention page at:
http://cancernet.nci.nih.gov/
*source: The National Cancer Institute
