A new study that compared the newer drug, letrozole, to the widely used tamoxifen found that the former was more effective. The study confirmed that survival rates for postmenopausal women, who are suffering from breast cancer and have undergone surgery, taking letrozole (Femara) are higher than that taking tamoxifen. Both letrozole and tamoxifen have been used to prevent recurrence of breast cancer in postmenopausal women with hormone receptor-positive cancer.