Endocrine Therapy for Breast Cancer

Breast cancer is the second most common cancer in Korean women and its mortality rate has increased steadily. Although breast cancer is heterogeneous tumor, hormone receptor-positive tumors comprise about 75 percent of all breast cancers. Therefore endocrine therapy that works by targeting estrogen receptor is a pivotal treatment for breast cancers. There are selective estrogen receptor modulators, such as tamoxifen and raloxifene, aromatase inhibitors, such as anastrozole, letrozole and exemestane, fulvestrant and luteinizing hormone-releasing hormone agonists used in endocrine therapy. Endocrine therapy is effective in treating early breast cancer as an adjuvant therapy and metastatic breast cancer as a palliative therapy. Also in women who are at high risk for breast cancer, tamoxifen or raloxifene can prevent breast cancer. Studies for neoadjuvant endocrine therapy are emerging. Considering side effects of each drug and overcoming drug resistance are needed to maximize effectiveness of treatment and advance endocrine therapy.