Medical technology4 min read

Liquid biopsy

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A liquid biopsy looks in blood or other body fluids for biomarkers shed by cancer cells, instead of taking a piece of the tumour. Some tests are FDA-approved for specific uses, such as guiding treatment for certain cancers and a blood test for colorectal cancer screening.

A liquid biopsy may be used if a biopsy of the tumour cannot be taken safely. In 2020 the FDA approved a test that analyses cell-free DNA in plasma as a companion diagnostic to identify mutations in the BRCA1 and BRCA2 genes, and on 26 July 2024 it approved a blood test for colorectal cancer for average-risk adults aged 45 and over.

In a study of 7,861 people, the approved colorectal cancer blood test detected cancer in 83% of cases, but about 1 in 10 people without advanced changes gets a false-positive result, and a negative result does not guarantee that cancer is absent. As for "multi-cancer detection" tests, the FDA has not approved any, and none has been shown to reduce cancer deaths.

Where it stands today — maturityApproved for specific uses¹²³

In widespread clinical use
Approved for specific uses
In clinical trials
Preclinical
Concept

Specific tests are FDA-approved for specific uses, whereas multi-cancer detection tests are not approved.

Companion tests for selecting treatmentApproved for specific uses
In 2020 the FDA approved a plasma test to identify BRCA1 and BRCA2 mutations to guide treatment.¹
Colorectal cancer blood testApproved for specific uses
Approved in July 2024 for average-risk adults aged 45 and over.²
Detecting multiple cancers with a single blood testIn clinical trials
The FDA has not approved any test of this type, and none has been shown to reduce deaths.³⁴

Status last checked: 2026-10-08 · What the maturity levels mean

What is it?

Liquid biopsies are biomarker tests that look in the blood or other fluids for markers coming from cancer cells.

How does it work?

Some detect DNA mutations that occur in cancer cells, from cell-free DNA isolated from plasma.

Where is it used today?

It may be done if a biopsy of the tumour cannot be taken safely.

In July 2024 the FDA approved a blood test for colorectal cancer for average-risk adults aged 45 and over; see also Routine screening by age.

Limits and risks

A negative result on the approved colon cancer blood test does not guarantee that cancer is absent, and about 1 in 10 people without advanced changes gets a false-positive result.

The FDA has not approved any test to detect multiple cancers, and none has been shown to reduce deaths; in published research, cancer was not found in more than half of cases with a positive result.

Common questions

Does the blood test replace a colonoscopy?

Only the doctor can decide that; the approved test may give false-positive results, and its negative result does not guarantee that cancer is absent. See How to read risk numbers.²

Questions for your doctor

Which test is best for me to detect colorectal cancer, and what are the limits of each option?
What does a positive or negative result mean in this specific test?

References

1
U.S. FDA. FDA Approves Liquid Biopsy Next-Generation Sequencing Companion Diagnostic Test. www.fda.gov/drugs/drug-approvals-and-databases/fda-approves-liquid-biopsy-next-generation-sequencing-companion-diagnostic-test
Health agencies & guidelines · Accessed 2026-10-08
2
U.S. FDA. Shield – P230009. www.fda.gov/medical-devices/recently-approved-devices/shield-p230009
Health agencies & guidelines · Accessed 2026-10-08
3
National Cancer Institute (NIH). What Cancer Screening Tests Check for Cancer?. www.cancer.gov/about-cancer/screening/screening-tests
Health agencies & guidelines · Accessed 2026-10-08
4
National Cancer Institute (NIH). Questions and Answers about Multi-Cancer Detection Tests. prevention.cancer.gov/research-areas/networks-consortia-programs/csrn/q-a-about-mcd-tests
Health agencies & guidelines · Accessed 2026-10-08
5
National Cancer Institute (NIH). Biomarker Testing for Cancer Treatment. www.cancer.gov/about-cancer/treatment/types/biomarker-testing-cancer-treatment
Health agencies & guidelines · Accessed 2026-10-08

Review status: Edited content · Last updated: 2026-10-08

Change log

2026-10-08 — Page created.

Educational content only — no diagnosis, and no substitute for a clinician.