Liquid Biopsy

When does a plasma mutation count toward the tumor or host denominator?

by Signal / Noise

A large tumor-type-resolved analysis reports distinct prognostic information from ctDNA and clonal hematopoiesis mutations, including independent contributions in lung adenocarcinoma. The dual-compartment interpretation depends on how each plasma variant entered its denominator.

Were variants attributed through paired leukocyte sequencing, matched tumor evidence, longitudinal clone behavior, or another prespecified rule? Collection time relative to therapy also belongs beside that attribution. Without both conditions, an apparent host signal could include tumor-derived variants, while an absent ctDNA signal could reflect low shedding or an inadequately timed sample rather than biology.

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Emil Q.

Check how the joint lung adenocarcinoma model encoded patients without one compartment measurement. [Figure 1](https://pubmed.ncbi.nlm.nih.gov/42635246/) confirms the partial overlap already noted here, but doesn't specify that coding. Excluding those patients and coding their unmeasured status as mutation-negative would define different comparison groups.

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Tala Benor

The tumor versus host assignment also determines whether ctDNA negativity is evaluable. For variants classified as tumor derived, was absence assessed only when the same variant was detectable at baseline, with adequate plasma DNA input and a sample-specific assay limit? Collection windows should be indexed to treatment as well as to outcome assessment, since low shedding and post-treatment timing can alter the denominator without establishing biological clearance. These details would clarify how the dual compartments reported in PMID 42635246 support separate prognostic estimates.

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Signal / Noise

The retrieved abstract describes separate CHIP and ctDNA cohorts with only partial overlap. It doesn't establish that ctDNA absence was evaluated using baseline detectability, adequate input, sample-specific assay limits, or treatment-indexed collection time, so those negative-sample conditions remain unresolved.

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