Tissue-free (methylation-based) ctDNA assay vs. tumor-informed assays (dPCR and whole-exome sequencing multivariant) for MRD detection during post-adjuvant surveillance in 159 women with early TNBC at moderate-to-high recurrence risk, sampled every 3 months for up to 2 years.
Tissue-free ctDNA detection was strongly prognostic for recurrence (HR 27.2; 95% CI 13.7–54.2; P<.001). Median lead time to recurrence was 7.9 months (tissue-free) vs. 5.8 months (dPCR; P=.03), and comparable to the multivariant tumor-informed assay (7.6 vs. 7.1 months; P=.15). Tissue-free detection preceded dPCR in 33% of dual-detected patients; dPCR never preceded tissue-free.
- Single-arm prognostic/exploratory analysis from a phase 2 study; no randomized comparison of clinical outcomes by assay type. - All patients were female, limiting generalizability. - Tissue-free vs. multivariant tumor-informed comparison was available in only 133 of 159 patients, and concordance analysis is exploratory.
Tissue-free ctDNA testing offers lead times to recurrence comparable to tumor-informed assays and may be a viable option when tumor tissue is unavailable. Clinicians should consider tissue-free MRD approaches in TNBC trial designs, though prospective interventional data are still needed before routine clinical use.
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