This study examines the effect of randomized breast screening trials on the incidence of advanced-stage diseases and the subsequent breast cancer death rate. It shows that when there was a 20% reduction in the incidence of advanced-stage disease, breast cancer mortality was reduced by 28%. When there was less than a 10% reduction in the incidence of advanced-stage disease, breast cancer mortality was not reduced. Overall, breast cancer mortality can be reduced when screenings are more effective in reducing advanced-stage breast cancer. More effective screening may require the use of MRI and 3D tomography for women with dense breast tissue.