Role of aromatase inhibitors in advanced breast cancer.

A number of potent and selective non-steroidal aromatase inhibitors are now available for treatment of advanced breast cancer in postmenopausal women, of which anastrozole and letrozole, in particular, represent a significant advantage over the earlier agents in terms of both efficacy and tolerability. These agents are rapidly becoming established as the second-line therapy of choice in postmenopausal women with advanced disease, progressing on tamoxifen, and data on their efficacy as first-line treatment compared with tamoxifen will be available in the near future. Exemestane, a new, steroidal aromatase inhibitor which potentially lacks cross-resistance with non-steroidal agents is still in clinical development. The full potential of the new-generation aromatase inhibitors in the treatment of breast cancer is currently being investigated in a large program of clinical trials evaluating their use as adjuvant treatment following surgery in postmenopausal patients with early disease.