Key Findings
- Analysis of 27,979 breast cancers profiled by Caris identified ESR1 amplification as a rare genomic alteration enriched in Luminal B disease.
- ESR1-amplified tumors exhibited genomic instability and enrichment of proliferative signaling pathways, including G2M checkpoint and MYC target gene sets.
- Clinically, ESR1 amplification was associated with reduced overall survival and shorter palbociclib time on treatment, supporting its potential role as a negative predictive biomarker for CDK4/6 inhibition.
- In this study, large real-world clinico-genomic analysis was used to identify rare molecular subsets associated with therapeutic resistance and clinically relevant treatment stratification in breast cancer.