The BCPT, part of the National Surgical Adjuvant Breast and Bowel Project (NSABP), began in April 1992 to determine whether the nonsteroidal, anti-estrogen drug tamoxifen could reduce the incidence of breast cancer in women who were at high risk for development of the disease. Only women who were at increased risk for developing breast cancer participated in the study. They were chosen based on their breast cancer risk as determined by a computer calculation that included specific factors.
By September 1997, more than 13,000 women had participated in the study. Data showed the results of tamoxifen treatment to be highly significant with a 49% reduction in the number of invasive breast cancers seen across all age groups. These results were confirmed in the final report issued in 2005.
The data were then turned over to the Endpoint Review, Safety Monitoring, and Advisory Committee for review of the toxicity, adverse side effects, and effectiveness of tamoxifen. This independent committee (whose members are not affiliated with either the NSABP or BCPT) concluded that the overall benefits of treatment with tamoxifen outweighed the overall risks.
Tamoxifen is one of the most widely prescribed cancer drugs in the world, and has been the focus of research on its actions, benefits, and risks for more than 30 years. Still, tamoxifen therapy may not be appropriate for all women who are at increased risk for breast cancer.
Before tamoxifen is prescribed, a woman and her doctor should take into consideration her age, personal history, and family history. She and her doctor should also weigh the benefits and risks of tamoxifen.
The use of tamoxifen is reportedly associated with some infrequent, but potentially life-threatening side effects. Endometrial cancer, pulmonary embolism, and deep vein thrombosis are conditions that may be caused or adversely affected by tamoxifen. Other common side effects include fatigue, which may go away after taking the drug for a few weeks, and hot flashes.