Advancements in Hormone Receptor-Positive Metastatic Breast Cancer - Episode 2
Navigating Treatment After Progression: Testing, ESR1 Mutations and Tolerable Options
May 5, 2025
Panelists discuss how to approach second-line therapy decisions for patients with metastatic breast cancer, emphasizing the importance of biomarker testing, including ESR1 mutations, and considering patient-specific factors.
Clinical Brief: Biomarker Testing Strategy in Second-Line Therapy
Main Discussion Topics:
- Strategic approach to biomarker testing when transitioning to second-line therapy
- Importance of liquid biopsy versus tissue biopsy for ESR1 mutation detection
- Role of PIK3CA and other pathway mutations in treatment selection
- Shared decision-making process for selecting between multiple treatment options
- Clinical assessment of endocrine sensitivity duration as a treatment predictor
Key Points for Physicians:
- Liquid biopsy preferred for ESR1 mutation detection due to subclonal nature (15%-20% better detection)
- PIK3CA mutations are clonal and detectable in the initial tissue biopsy
- Prior CDK4/6 inhibitor response duration greater than 12 months indicates endocrine sensitivity
- Multiple treatment options require individualized patient assessment
- Quality-of-life considerations balance with efficacy outcomes
The discussion emphasized that endocrine resistance is a complex phenomenon involving multiple pathways, not just ESR1 mutations, requiring comprehensive biomarker assessment for optimal treatment selection.
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