Liquid Biopsy Research

What "liquid biopsy" means

A liquid biopsy looks for traces of a tumor in a blood sample instead of removing a piece of the tumor. Cancer cells shed small fragments of DNA into the bloodstream, and this circulating tumor DNA (ctDNA) is the most common thing these tests measure. [1] The phrase covers very different tests with different jobs, so "liquid biopsy" on its own tells you almost nothing about whether a specific test is proven for a specific purpose.

Evidence labels used on this page: approved medicine or approved test (the regulator and indication are named), established, promising but limited, insufficient evidence, and marketing claim. Status is given per exact test and indication, because approval for one purpose does not carry over to another.

Four different jobs, four different levels of evidence

Matching treatment in advanced cancer

This is where liquid biopsy has the clearest regulatory footing. A companion diagnostic is a test that provides information essential for the safe and effective use of a particular drug. [2] The US FDA's list names specific blood-based tests for specific drugs. For example, one plasma test is listed for a lung cancer drug (osimertinib) tied to certain EGFR changes, and another plasma test is listed for a prostate cancer drug (talazoparib). [2] A published review notes that most current clinical use of ctDNA aims to find drug-targetable and drug-resistance mutations, mostly in metastatic disease. [1]

Two cautions apply. First, these approvals name exact test-drug-cancer combinations; they do not mean any blood test can guide any cancer treatment. Second, not every change found in blood comes from a tumor. Clonal hematopoiesis, a normal age-related process in which blood-forming cells acquire mutations, can create signals that look like tumor mutations, and mistaking them for tumor DNA could lead to inappropriate treatment. [3]

Blood test for colorectal cancer screening

In July 2024 the FDA approved the Shield test (decision date 07/26/2024) for colorectal cancer screening in people at average risk, age 45 or older. [4] The FDA's approval statement says a positive result should be followed by colonoscopy and that the test is not a replacement for diagnostic colonoscopy or for surveillance colonoscopy in high-risk individuals. [4]

In the company-funded ECLIPSE study, the test detected 83.1% of colorectal cancers but only 13.2% of advanced precancerous lesions, and 89.6% of people without advanced neoplasia had a negative result. [5] Detection of advanced precancerous lesions is the notable gap, and it shows why an "approved" status still needs the indication and performance read closely. How it compares with other screening tests, and when your care team might suggest each, is a conversation for your clinician.

Monitoring for leftover cancer after surgery

This use is called minimal residual disease testing. Reviewers describe ctDNA as a candidate marker in the curative setting that is still being evaluated. [1] The strongest human evidence here comes from DYNAMIC, a randomized trial in stage II colon cancer with 455 patients: 302 had decisions guided by ctDNA and 153 by standard features. [6] Chemotherapy was used less often in the ctDNA group (15% versus 28%) without worse 2-year recurrence-free survival. [6] At 5 years, recurrence-free survival was 88% with the ctDNA-guided approach and 87% with standard management. [7]

What this shows and does not show: one specific assay strategy, in one cancer type and stage, reduced treatment without harming recurrence outcomes. It does not show that every ctDNA test works in every cancer. Status: promising but limited; We did not find a regulator record supporting an approval for a residual-disease claim, so treat any specific commercial claim as not verified until you see the regulator's own record.

Screening healthy people for many cancers

Blood tests that look for signals from many cancers at once are covered on the multi-cancer early-detection page and, from the longevity angle, in cancer screening and multi-cancer detection tests. The evidence standard for screening people with no symptoms is higher than for monitoring someone with known cancer, because false alarms and unnecessary follow-up affect many healthy people.

Questions to ask about any liquid biopsy claim

• Which exact test, and for which cancer and purpose is it approved or validated?
• Was it studied in people like me (with or without a cancer diagnosis)?
• What happens after a positive or a negative result, and what does a negative result not rule out?
• Did the study measure outcomes that matter (survival, avoiding harm), or only whether the test finds a signal? See biomarkers vs clinical outcomes.