stromectol effets secondaires Tamoxifen has been used extensively in the treatment of both advanced stage and early stage estrogen receptor ER positive breast cancers and was recently approved as a chemopreventive agent for women at high risk for breast cancer 1, 2 The observed clinical efficacy of tamoxifen has been associated with its ability to induce growth arrest and apoptosis in breast cancer cells through the inhibition of estrogen binding to the ER