Beelen K, et al. - In the present study, researchers assessed the value of Ki67 protein expression and other proliferation markers for predicting if tamoxifen would be effective for postmenopausal breast cancer subjects. The findings from the present study suggested that postmenopausal breast cancer patients with high Ki67 counts do see significant benefit from adjuvant tamoxifen. On the other hand, those with high mitotic count do not. The study results showed that mitotic count was a better selection marker for reduced tamoxifen benefit vs Ki67.