[Recent advance of hormonal treatment for breast cancer]

Since ER positivity in breast cancer is highest in the early stage of its natural history, hormonal treatment should be given as the initial treatment after both surgery and recurrence. Tamoxifen and medroxyprogesterone acetate have been commonly used as the standard hormonal treatment with a response rate of 20-30% and a median duration of response of 6-10 months. New agents for hormone therapy include tamoxifen analogues, LH-RH analogues and aromatase inhibitors. They are now on or have just cleared phase studies. LH-RH analogue is a unique drug that is active for premenopausal patients and should be used as the first-line therapy for them. Aromatase inhibitors lower serum estrogen levels by inhibiting conversion from andreogens to estrogens, thus inducing regression of ER-positive tumors. They are used as the second-line treatment after tamoxifen failure for postmenopausal patients. An increasing body of information has been accumulated as to how the hormonal treatments affect breast cancer at subcellular levels. New approaches controlling growth factors such as anti-angiogenesis are under way.