Estrogen Receptor Antagonists After Progression in ER-Positive, HER2-Negative Metastatic Breast Cancer

In this segment, Dr. Gregory Vidal discusses the role of estrogen receptor antagonists in the treatment of ER-positive, HER2-negative metastatic breast cancer following progression on prior endocrine therapy. He explains that when disease progression occurs, repeat biomarker testing may identify molecular changes such as ESR1 mutations, which can influence the next line of therapy. Dr. Vidal outlines how oral selective estrogen receptor antagonists, including elacestrant and imlunestrant, may be considered in appropriate clinical settings, particularly when tumor biology suggests continued dependence on estrogen receptor signaling. He emphasizes that treatment selection is individualized and based on prior therapies, biomarker findings, disease burden, and patient-specific factors. The goal remains to control disease progression while maintaining quality of life. This segment reinforces the importance of reassessing tumor biology after progression and highlights how advances in targeted therapies continue to expand treatment options for patients with ER-positive, HER2-negative metastatic breast cancer.