New Insights in Estrogen Receptor (ER) Biology and Implications for Treatment

Purpose of Review Estrogen receptor-positive (ER+) breast cancer represents the majority of breast cancer diagnoses and is the leading cause of cancer death in women. Endocrine therapy is the principal treatment strategy for ER+ breast cancer. However, resistance to endocrine therapy, either de novo or acquired, is commonly observed, resulting in disease relapse and progression. This review will focus on recent progress in our understanding of ER biology and the implications for treatments.