[Aromatase inhibitors: a review of clinical trials].

To increase the therapeutic index of second line hormonal treatment of breast cancer, new aromatase inhibitors have been synthetized; they belong to two groups: type I (formestane and exemestane) are steroidal irreversible and specific inhibitors, type II (anastrozole, letrozole and vorozole) are non steroidal reversible inhibitors, interfering with the aromatase heme. Several phase II and III trials demonstrated that these drugs are, at least, as active as aminoglutethimid or progestins in second line treatment, and are less toxic. Recently, an identical activity have been observed for anastrozole and tamoxifen in first line. In metastatic and adjuvant settings, large trials are ongoing to clarify the exact value of these drugs.