Current status of endocrine therapy for breast cancer

Endocrine therapy is usually indicated prior to chemotherapy as the first line therapy for metastatic breast cancer patients because of its milder toxicity. Patients who respond to a first-line endocrine therapy have a high chance of responding to a second-line endocrine therapy, and thus the responders to a first-line endocrine therapy would better be treated with second or third-line endocrine therapy. In the adjuvant setting, tamoxifen (antiestrogen) has been proven to improve the prognosis of both pre- and postmenopausal estrogen receptor positive breast cancer patients, and goserelin (LH-RH agonist) has been proven to improve prognosis in premenopausal women comparable to chemotherapy (CMF). Very recently, preliminary results have indicated that anastrozole (aromatase inhibitor) is superior to tamoxifen as adjuvant treatment for estrogen receptor positive postmenopausal breast cancer patients. In addition, the recent success of tamoxifen in a chemoprevention trial seems to have ushered in a new era wherein prevention of breast cancer is much more emphasized than treatment of established breast cancer.