Superior Efficacy of Letrozole Versus Tamoxifen as First-Line Therapy for Postmenopausal Women With Advanced Breast Cancer: Results of a Phase III Study of the International Letrozole Breast Cancer Group

To compare the efficacy and tolerability of tamoxifen with that of letrozole, an oral aromatase inhibitor, with tamoxifen as first-line therapy in postmenopausal women with advanced breast cancer.Nine hundred seven patients were randomly assigned letrozole 2.5 mg once daily (453 patients) or tamoxifen 20 mg once daily (454 patients). Patients had estrogen receptor- and/or progesterone receptor-positive tumors, or both receptors were unknown....