Endocrine Therapy for Advanced Breast Cancer: Beyond Tamoxifen and Aromatase Inhibitors

Treatment options for hormone-dependent advanced breast cancer (BC) have evolved from surgical oophorectomy, first proposed over a century ago. The discovery of steroid hormones, steroid hormone receptors and the concept that inhibition of steroid biosynthesis or hormone receptor blockade prevents tumor growth, have been introduced and tested clinically. Today, the aromatase inhibitors are the current standard of care for metastatic hormone-sensitive BC in postmenopausal women. To get to this point, many others drugs have been investigated in the continuing search for improved treatment of advanced BC. Agents as high dose estrogens, progestins, antiprogestins, androgens and somatostatin analogues were tested time ago and novel and promising agents, as fulvestrant or sulfatase inhibitors are currently going through a comprehensive clinical trial program. By reviewing the clinical data on the endocrine therapy of advanced BC, we project those areas of future clinical research, beyond the well-known and established tamoxifen and aromatase inhibitors.