1. Preanalytics is part of the result
Specimen type, fixation time, tumour-cell fraction, necrosis and block age change sensitivity. Plasma ctDNA yield depends on tumour burden and metastatic biology. ‘Not detected’ is therefore hard to interpret without specimen details.
2. One NGS assay does not see everything equally
Short variants, large rearrangements, amplifications, fusions, MSI, TMB and HRD require different analytical solutions. RNA sequencing is often stronger for fusions; IHC/ISH remain standard for several protein and amplification biomarkers.
3. The finding must be exact
The report needs HGVS, genome build, allele fraction, coverage, copy number or an exact fusion name; partners and breakpoints are reported when the assay can resolve them. ‘EGFR+’, ‘BRCA-mutated’ or ‘HER2 altered’ is insufficient: variants in one gene can mean sensitivity, resistance, inherited risk or no proven action.
4. Evidence is ranked, not guessed
AMP/ASCO/CAP classifies somatic clinical significance, while ESCAT ranks target actionability. Approval in another tumour, a single case or a preclinical model must be labelled below randomised evidence in the same indication.
5. A biomarker does not prescribe a drug
A decision depends on morphology, stage, line, prior treatment, performance status, organ function, interactions, access and current authorisation. Conflicting signals and rare variants are best reviewed by a molecular tumour board.
6. Negative results also have boundaries
The report should state what was excluded at the assay’s sensitivity. Non-informative ctDNA requires tissue reflex when feasible. Repeat biopsy may be needed after tumour evolution, but only when the result can change a safe decision.