Results of that trial were announced in 1998. That same year, the Food and Drug Administration approved tamoxifen as a preventive agent in women at high risk for breast cancer. This is an important study because previous research suggests both tamoxifen and raloxifene may reduce breast cancer risk.
More research is needed to determine which drug is most effective and has the fewest side effects.
Tamoxifen has been used for more than 20 years as a therapy to treat breast cancer. It works, in part, by interfering with the activity of estrogen, the female hormone that promotes growth of breast cancer cells. The BCPT was launched after research and treatment with tamoxifen suggested it also could reduce breast cancer occurrence. The study enrolled women at high risk for breast cancer because of age, a family history or their own medical history. After three years, the researchers found the group taking tamoxifen had a 49 percent decrease in the incidence of breast cancer compared to the group taking the placebo.