Aromatase inhibitors in breast cancer.

Estrogens play important roles in breast cancer development and progression. In postmenopausal women, traditional endocrine therapies such as tamoxifen have sought to inhibit estrogen action by targeting the estrogen receptor itself. However, newer treatments are evolving that target estrogen production in postmenopausal tissues through inhibition of the aromatase enzyme. Clinical data demonstrate that these aromatase inhibitors are superior to tamoxifen as adjuvant therapy for breast cancer and have now replaced tamoxifen as first line therapy in a number of treatment regimens for postmenopausal breast cancer patients.