What liquid biopsy is
A blood test that looks for tumour-derived material circulating in the bloodstream. It provides molecular information without a tissue procedure.
Liquid biopsy
A blood sample can provide molecular clues.
Liquid biopsy has genuinely widened what is possible in molecular oncology. It also has clear limits, and both matter when deciding whether to use it.
The pathway
From blood sample to interpretation.
- 01Blood sample
- 02ctDNA isolation
- 03Sequencing
- 04Molecular profile
- 05Clinical interpretation
Circulating tumour DNA (ctDNA)
Tumours can shed fragments of DNA into the blood. Sequencing those fragments may reveal alterations present in the tumour, depending on how much ctDNA is present.
Where it may be applied
Characterising advanced disease when tissue is insufficient, re-assessing molecular status at progression, and — in selected situations — monitoring molecular change over time.
Advantages
Minimally invasive, repeatable, quicker to obtain than a new biopsy, and able to sample material from more than one disease site.
Limitations
Sensitivity depends on how much tumour DNA is circulating. A negative result does not exclude an alteration. Some findings need confirmation, and structural or histological questions cannot be answered from blood.
When it may be considered
When tissue is unavailable or inadequate, when a procedure carries meaningful risk, when a rapid answer would change a decision, or when molecular status may have changed.
Why tissue biopsy may still be necessary
Histological diagnosis, tumour morphology, immunohistochemistry and several biomarkers require tissue. Liquid biopsy complements tissue biopsy; it does not replace it in every case.
Discuss whether blood-based testing fits your clinical situation.
Existing reports can be reviewed before anything new is recommended.