Tamoxifen is a drug that binds to your estrogen receptors. Therefore it was thought that it could prevent excess estrogen binding, hence halting cancer from forming.
It is generally prescribed to high-risk women to prevent breast cancer, and is usually taken for five years.
However, Tamoxifen has been found to cause cancer instead. According to a study published in the International Journal of Gynecological Cancer, the treatment of breast cancer with tamoxifen results in an increased risk of uterine cancer incidence and mortality.
This is just one in a growing line of studies published, raising serious concerns about the increased risk of uterine cancer for women who take tamoxifen as a cancer preventive drug.
Despite these concerns, tamoxifen is still on the market.
International Journal of Gynecological Cancer 2007