Breast cancer and duration of tamoxifen.

Two randomised trials have compared 5 years versus 10 years of tamoxifen therapy following surgery for hormone receptor-positive early breast cancer. Overall mortality, breast cancer-related mortality and the breast cancer recurrence rate were all lower when tamoxifen was continued for 10 years. Prolonging tamoxifen therapy increased the incidence of endometrial cancer and thromboembolic events. The value of tamoxifen therapy therefore decreases over time.