New directions in hormone therapy for metastatic breast cancer.

• Nonsteroidal, type II (reversible) anti-aromatases, termed aromatase inhibitors. The first clinically available drug, aminoglutethimide (AG), belongs to this class. Aminoglutethimide is nonspecific and requires patients to associate a corticosteroid. Two newer, more specific agents that are administered orally and act solely on aromatase have been tested: letrozole (Let) (2.5 mg/day) and anastrozole (Ana) (1 mg/day). • Steroidal, type I (reversible) anti-aromatases, also known as aromatase inactivators. The major representative of this class is exemestane (Exe), which is administered per os (25 mg/day).