Liquid biopsy

A diagnostic test that detects and analyzes disease-associated material in blood or another bodily fluid. In cancer care, it can reveal tumor-derived DNA, cells, or other biomarkers without sampling tumor tissue directly.

Circulating tumor DNA: Short DNA fragments shed by tumor cells into bodily fluids, especially blood. Tumor-derived DNA is a major signal measured in cancer-focused liquid biopsies.
Cancer screening: Testing asymptomatic people to detect cancer before symptoms appear. Blood-based tests are being developed to screen for multiple cancers, though population benefit remains under study.
Tissue biopsy: A procedure that removes tissue from the body for microscopic or molecular examination. It samples tumor directly, whereas liquid biopsy uses material shed into fluids.
Clinical utility: The extent to which a test improves health outcomes or clinical decisions in practice. A detectable biomarker matters only if acting on it benefits patients.
Biomarker: A measurable biological feature that indicates a normal process, disease process, or response to an intervention. Liquid biopsy detects biomarkers that may indicate cancer or another disease.
Circulating tumor cells: Cancer cells that detach from tumors and travel through the bloodstream. Their capture can provide intact cells for analysis rather than isolated tumor fragments.
Minimal residual disease: A small number of cancer cells that remain after treatment and may later cause relapse. Serial tumor-DNA testing can seek residual disease that imaging cannot yet reveal.
Fine-needle aspiration: A procedure that collects cells through a thin needle for diagnostic examination. It obtains cells from a specific lesion but can be invasive or yield limited material.
Lead-time bias: An apparent increase in survival caused by earlier diagnosis without delaying death. Earlier detection by blood tests can lengthen measured survival without changing disease outcome.
Polymerase chain reaction: A laboratory technique that makes many copies of selected DNA sequences. PCR-based methods amplify target sequences before or during liquid-biopsy analysis.

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