The Galleri Cancer Blood Test: What the First Big Trial Found, and What It Means for You
By Andres Zuleta, MD, ThriveMed · Patient education
A blood test that looks for signs of many cancers at once sounds like the screening test everyone has been waiting for. On September 22, 2026, the first large randomized trial of one of these tests, Galleri, was published in the New England Journal of Medicine, along with two papers in Nature Medicine on how well the test performed.
The honest answer is mixed. Below, I walk you through the trial, the results, the drawbacks and the possibilities, in plain language, and the three questions I would bring to your next visit.
The short version
The trial: 142,250 people aged 50 to 77 in England took part. Half had their blood tested once a year for up to three years.
The results: false alarms were rare, and about half of positive results turned out to be cancer. The test caught about 1 in 3 cancers overall, and about half of 12 cancer types behind most cancer deaths.
The drawbacks: the trial's main goal, fewer late-stage cancers, was not met. The test is not FDA approved, the company that makes it funded the studies, and a negative result does not rule out cancer.
The possibilities: it could someday help find cancers that have no screening test today.
Your next step: keep up with your proven screenings, and talk it through with your doctor.
Watch: the Galleri studies in 5 minutes
Short on time? Watch the 48-second version on YouTube Shorts.
How the test works
Tumors shed tiny fragments of DNA into the blood. Galleri reads a chemical pattern on that DNA, called methylation, that tends to look different in cancer. A positive result says "cancer signal detected" and predicts where in the body the signal is coming from. It is not a diagnosis. It is a reason for more tests.
1. The trial
The trial is called NHS-Galleri, and it ran inside England's National Health Service. 142,250 people aged 50 to 77 gave blood once a year for up to three years. They were randomly split into two equal groups. In one group the blood was tested with Galleri; in the other it was stored untested. Both groups were encouraged to keep up their regular screenings.
The main goal was to see whether testing led to fewer cancers being found at a late stage (stage III or IV) among 12 prespecified cancer types.
2. The results
Late-stage cancers were not reduced. The rate of stage III or IV cancer was about the same in both groups (rate ratio 1.03, P = 0.63).
There was one possible signal. For stage IV alone, the rate ratio was 0.86, but the 95% confidence range runs from 0.74 to 1.00. Because it touches 1.00, which means no difference, it is not statistically significant. The authors say longer follow-up is needed.
How the test itself performed (Nature Medicine):
About 1 in 100 people got a positive result in each round.
When the test was positive, about half of people had cancer: 58.0% in round one, falling to 45.8% by round three.
False alarms were rare. Specificity was 99.5% to 99.6%, which works out to a false alarm in about 1 in 200 people without cancer, or fewer.
It caught about 1 in 3 cancers overall (26.7% to 37.2% of cancers diagnosed within a year). For 12 cancer types that cause more than 60% of cancer deaths, it caught about half (47.6% to 63.4%). Prostate and breast cancers were the ones most often not flagged.
A second study, PATHFINDER 2, followed 35,878 adults aged 50 and older, mostly in the US. A positive result was right 60.3% of the time, sensitivity was 39.3%, and 185 people were screened to find one cancer. 0.6% had an invasive procedure after a positive result, mostly not surgery.
3. The drawbacks
I want you to have the full picture, not just the headline.
The main goal was not met. Testing did not lower the rate of late-stage cancer in this trial.
The company paid for the research. GRAIL, which makes the test, funded all three studies and took part in writing them.
No survival data yet. We do not know whether testing lowers the chance of dying from cancer. Those results will come in future papers.
A negative result does not rule out cancer. Many cancers, especially prostate and breast, were not flagged.
It does not replace your proven screenings: colonoscopy, mammograms, Pap or HPV tests, and low-dose CT for lung cancer if you are eligible.
It is not FDA approved. On September 23, 2026, an FDA advisory panel voted 10 to 0 that it is safe, 6 to 4 that it is effective, and 7 to 2, with one abstention, that its benefits outweigh its risks for adults 50 and older. That is advice, not a decision and not peer-reviewed research. The FDA's decision is pending.
PATHFINDER 2 used an earlier version of the test than the one offered today.
4. The possibilities
Most proven screening tests look for one cancer at a time, and some of the deadliest cancers, like pancreas, liver and ovary, have no recommended screening test at all. In PATHFINDER 2, about 7 in 10 of the cancers the blood test found (72.8%) were types with no recommended US screening test.
That is why researchers are interested. A test like this could someday help find cancers we currently have no way to screen for. Could is the key word: we still need longer follow-up and data on cancer deaths before we know whether it helps people live longer.
Three questions to bring to your next visit
Am I up to date on the proven screenings for my age and history?
What is my personal risk, based on things like age, smoking and family history?
If I take this test, what is the plan for a positive result, knowing a negative does not clear me?
My opinion, not a finding of these studies: this could become a useful add-on one day. Today, it is a decision to make with your doctor, on top of your screenings, not instead of them.
If you want the more detailed, physician-level read of these papers, I wrote it on my own site: NHS-Galleri and PATHFINDER 2: my read of the first big multi-cancer blood test trial.
Sources
Sasieni P, et al. Effect of Screening with Multicancer Early-Detection Test on Late-Stage Cancer Diagnosis. New England Journal of Medicine, published online September 22, 2026. doi.org/10.1056/NEJMoa2505723
Neal RD, et al. Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial. Nature Medicine, 2026 (open access). doi.org/10.1038/s41591-026-04652-8
Nabavizadeh N, et al. Performance and safety of a multi-cancer early detection test: the PATHFINDER 2 study. Nature Medicine, 2026 (open access). doi.org/10.1038/s41591-026-04618-w
FDA advisory panel vote, September 23, 2026: GRAIL press release (company statement, not peer-reviewed).
This article is for education only and is not medical advice. Approximate figures ("about 1 in 3", "about 1 in 200") are rounded from the published numbers shown next to them.