It would be wonderful if it were possible just to take simple pill to greatly decrease the risk of developing breast cancer. There is no such pill at this time, but there is research aimed at developing such a treatment. One of the medicines being tested for this purpose is tamoxifen.
Tamoxifen is an anti-hormone.
Because many breast cancers need the female hormone estrogen to grow, it is hoped that tamoxifen will prevent them from starting. There is a national program to test whether tamoxifen will be safe and effective in preventing breast cancer. Half the women in this program will take tamoxifen, and the other half will take a placebo pill. This program will answer the question of whether tamoxifen, on average, causes net good or net harm in healthy women, but results won't be available for five to ten years.