Should aromatase inhibitors replace tamoxifen?

Six years ago, we reviewed the selective aromatase inhibitors, anastrozole and letrozole, for the treatment of women with breast cancer. We concluded that anastrozole was at least as effective as megestrol (the standard treatment at that time for women with advanced postmenopausal breast cancer in whom tamoxifen had failed), but that there was insufficient published evidence to decide the place of letrozole in therapy. Since then, these drugs have become standard second-line treatment options for postmenopausal women with locally advanced or metastatic, hormone-receptor-positive breast cancer, and a third selective aromatase inhibitor, [symbol: see text] exemestane (pronounced eks-ee-mes-tane), has been added to the market. Here we consider whether the aromatase inhibitors should replace tamoxifen as first-line therapy.