Endocrine Abstracts

Estrogen receptor alpha (ER) and progesterone receptor (PR) are widely used predictive and prognostic biomarkers in breast cancer. ER is also a well-established therapeutic target. A major unresolved clinical issue is the development of therapy resistance, especially to ER-targeted therapies. We, and others, have observed somatic ESR1 mutations in up to 40% of metastatic tumors obtained from women who have acquired resistance to endocrine therapies. The two most common mutatio...