Efficacy of tamoxifen as treatment of breast cancer.

The synthetic antiestrogen tamoxifen was developed by ICI Pharmaceuticals (now Zeneca) in 1969 as a possible oral contraceptive and later was shown in clinical trials to be an effective treatment against advanced breast cancer. Since that time, millions of women have received tamoxifen as therapy for metastatic breast cancer as well as adjuvant treatment following surgery for primary breast cancer. Based on the data evaluated to date, adjuvant tamoxifen treatment for 2 to 5 years following primary treatment is associated with a 30% reduction in the odds of recurrence and a 20% reduction in the odds of death each year for at least 10 years. In addition, data from studies suggest that tamoxifen could have a small possibly beneficial effect on noncancer mortality.