Differential impact of tumor-derived ESR1 mutations on elacestrant benefit in metastatic breast cancer

Abstract Background: ESR1 mutations are a well-established mechanism of endocrine therapy resistance in estrogen receptor (ER)-positive metastatic breast cancer and are a biomarker for treatment benefit from oral selective estrogen receptor degraders (SERDs) such as elacestrant. However, variant-specific and context-dependent effects on therapy response remain poorly understood.