Optimizing ESR1 Mutation Testing Strategies in HR-Positive, HER2-Negative Advanced Breast Cancer

Dr. Jason Mouabbi and Dr. Seth Wander discuss current approaches to biomarker testing and ESR1 mutation detection in patients with HR-positive, HER2-negative advanced breast cancer. Dr. Wander highlights the importance of genomic testing at the time of metastatic diagnosis, including the use of tissue-based testing and liquid biopsy approaches to identify actionable alterations. The discussion explores differences between tissue and circulating tumor DNA testing, including how liquid biopsy may capture tumor heterogeneity and acquired resistance mechanisms such as ESR1 mutations. Dr. Wander describes his current clinical approach of utilizing baseline molecular profiling and reassessing with liquid biopsy at the time of disease progression to identify emerging targetable alterations. The experts also discuss how evolving clinical evidence may influence future approaches to monitoring ESR1 mutations during treatment and integrating biomarker-guided strategies into clinical practice.