# Utility of circulating tumor DNA in cancer diagnostics with emphasis on early detection

Source: https://onco.cc/key-papers/paper-fiala-ctdna-early-detection-bmc-med-2018/  
OnCo record `paper-fiala-ctdna-early-detection-bmc-med-2018` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A review that works out how many genome copies a blood sample holds, and why very small tumour fractions run out of molecules to find.

## Summary

A review of circulating tumour DNA in diagnostics. Its full text states that most studies cite cell-free DNA in normal individuals at 1 to 10 ng per mL (average 5 ng per mL), that 5 ng of DNA equates to approximately 1,500 genomes, and that when the tumour fraction falls below 0.01 per cent a 10 mL blood draw (4 mL of plasma) will likely not contain a single cancer genome at a given locus, so detection becomes impossible through sampling error alone.

## Fields

- Kind: Key paper
- Last checked: 2026-11-04
- Journal: BMC Medicine
- Year: 2018
- DOI: 10.1186/s12916-018-1157-9
- Authors: Fiala C, Diamandis EP
- Findings: Cell-free DNA 1 to 10 ng/mL, average 5 ng/mL.; 5 ng of DNA is approximately 1,500 genomes.
- What it means: The number of molecules in the tube, not the sequencer, sets the floor for any single-locus blood test; multi-locus tests escape it only by adding sites together.
- Caveats: The argument is for a single locus in screening; residual disease tests track many loci.

## Sources

- Fiala and Diamandis, BMC Med 2018: https://doi.org/10.1186/s12916-018-1157-9
- PubMed: https://pubmed.ncbi.nlm.nih.gov/30285732/

## Connected records

- fronts: [Diagnostics & Biomarkers](https://onco.cc/fronts/diagnostics/)
- technologies: [Liquid biopsy (ctDNA)](https://onco.cc/technologies/liquid-biopsy/)
- terms: [Cell-free DNA (cfDNA)](https://onco.cc/terms/cfdna/), [Circulating tumour DNA (ctDNA)](https://onco.cc/terms/ctdna/)
- bottlenecks: [Naming which clone or phenotype is left after treatment](https://onco.cc/bottlenecks/b-subclone-attribution-residual-disease/)

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