ESR1 and PIK3CA circulating tumor DNA (ctDNA) mutation status as predictive biomarkers beyond variant allele fraction (VAF) in metastatic breast cancer.
Understanding which genetic mutations matter in metastatic breast cancer blood tests—not just their amount—clarifies how to sequence newer precision therapies effectively.
This Journal of Liquid Biopsy review clarifies a critical clinical point: in HR+/HER2- metastatic breast cancer, the presence or absence of ESR1 and PIK3CA mutations in ctDNA — not the variant allele fraction — is the validated criterion for therapeutic decisions, supported by multiple pivotal trials (EMERALD, PADA-1, SERENA-6, SOLAR-1, BYLieve, INAVO120, CAPItello-291). The authors explain why direct VAF comparison across these biomarkers is biologically inappropriate given their different evolutionary roles (ESR1: acquired subclonal under endocrine therapy vs PIK3CA: early clonal driver), with practical implications for clinical report interpretation and therapy sequencing.
What the study was
- Study design
- review
- Population
- HR+/HER2- metastatic breast cancer patients receiving ESR1-directed or PIK3CA-directed therapy
- Category
- Early Detection
- Maturity
- Validated
- Journal
- J Liq Biopsy
Why it surfaced
Clinically actionable review addressing ctDNA interpretation in mBC; PMC open access (PMC13355476); Editor-in-Chief co-authorship; highly relevant to early cancer detection/liquid biopsy watchlist; pipeline_priority=HIGH per EARLY_CANCER_DETECTION flag rule despite triage_score 7.
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