Current clinical trials of endocrine therapy for breast cancer. 
Breast cancer is a hormone-dependent cancer like prostate cancer and endometrial cancer.  Estrogen plays important roles in the development and progression of breast cancer.  Endocrine therapy is the treatment of choice for estrogen receptor- and/or progesterone receptor-positive breast cancer.  Endocrine therapy has been used for several purposes, including chemoprevention, preoperative treatment, postoperative adjuvant treatment and treatment for recurrent diseases.  A large number of clinical trials have provided evidence showing the clinical benefits of various endocrine therapies for the treatment of breast cancer.  The current status and recent advances in endocrine therapy for breast cancer are reviewed based on the results of current clinical trials.  Future perspectives of endocrine therapy are also discussed.