The drug anastrozole (Arimidex) reduced the chance of developing breast cancer by 53% in postmenopausal women at high risk for the disease (40 women developed breast cancer in the anastrozole group, compared with 85 women in the placebo group), according to a study published online December 12 in The Lancet. Anastrozole works by lowering the amount of estrogen in the body, which some breast cancers need to grow. This medication belongs to the class of breast cancer drugs called aromatase inhibitors. In this study, anastrozole was more effective than older breast cancer drugs called selective estrogen receptor modulators (SERMs), which include tamoxifen (Nolvadex) and raloxifene (Evista). However, it was similar in effectiveness to another aromatase inhibitor, exemestane (Aromasin). An editorial in the same issue stresses that researchers still need to determine whether breast cancer prevention drugs actually reduce deaths from the disease, which studies have not yet shown.