Most cancers have no screening test at all. Routine screening exists for breast, cervical, colorectal, lung and, in some settings, prostate cancer, but pancreatic, ovarian, liver, stomach, esophageal and many other deadly cancers are usually found only when they cause symptoms, often at a late stage. Multi-cancer early detection tests aim to close that gap with a single blood draw. In September 2026, the two largest studies of the leading test were published on the same day. This article explains how these tests work, what those studies showed, and what the tests can and cannot do.
How the Tests Work
Cancer cells shed fragments of DNA into the blood. Cancer DNA carries distinctive chemical tags, called methylation patterns, that differ from those of normal cells, and the pattern also differs by tissue. The most studied test, Galleri, reads these patterns to detect a cancer signal and predict where in the body it came from, which guides the follow-up scans. Our article on ctDNA liquid biopsy explains circulating tumor DNA in more detail.
PATHFINDER 2: How Accurate Is a Positive Result?
PATHFINDER 2, published in Nature Medicine in September 2026, followed 35,878 adults aged 50 and older with no sign of cancer.1 Among those analyzed:
A positive result usually meant cancer. About 60 percent of people with a positive result were diagnosed with cancer, and the false-positive rate was below half a percent.
It found cancers that screening misses. Added to standard screening, the test increased the number of screen-detected cancers several-fold. Of the early-stage cancers it found, about 70 percent were types for which no screening test is recommended.
The origin prediction was usually right, which shortened the search for the cancer.
But it misses many cancers. The test detected about 39 percent of all cancers diagnosed during the following year, and about 70 percent of the twelve deadliest types it is designed to find. It frequently missed early breast and prostate cancers, which standard screening detects well.
NHS-Galleri: Does It Shift Cancer to Earlier Stages?
The more important question is whether screening with the test finds cancer early enough to change outcomes. The NHS-Galleri trial in England, which randomly assigned about 140,000 people to yearly testing or usual care, was designed to answer it. Its main results, published in the New England Journal of Medicine in September 2026, were mixed.2
The primary goal was not met. Three years of testing did not reduce the combined number of stage III and stage IV cancers.
There were encouraging signals. The tested group had about 14 percent fewer stage IV cancers, a difference at the edge of statistical significance, and about 20 percent fewer cancers diagnosed through emergency presentations, which tend to be advanced. Researchers noted that the first round of any screening program uncovers a backlog of cancers that are already advanced but have not yet caused symptoms, which may have hidden a benefit in later rounds.
Whether these tests ultimately reduce cancer deaths has not yet been shown.
What This Means in Practice
It adds to standard screening; it does not replace it. Mammograms, colonoscopy or stool and blood tests for colorectal cancer, low-dose lung CT for eligible smokers, and cervical screening remain essential.
A negative result does not rule out cancer. Symptoms always deserve evaluation, whatever a blood test says.
A positive result starts a search. It leads to scans and sometimes biopsies. In PATHFINDER 2, fewer than 1 percent of participants needed an invasive procedure, and most of those procedures were not surgical.
Who may benefit most. The case is strongest for people at higher risk, such as those over 50 with a strong family history or other risk factors, because the test is most likely to find something meaningful when cancer is more likely. Our book, The New Reality of Cancer, has a chapter on these tests and explains this reasoning in detail.
After a cancer diagnosis, a different test is better. For people who have already had cancer, tumor-informed circulating tumor DNA tests, built from the person’s own tumor, are far more sensitive for detecting recurrence. See our article on why cancer comes back.
Frequently Asked Questions
Is there a blood test that screens for many cancers?
Yes. Multi-cancer early detection tests such as Galleri look for cancer DNA in the blood and predict where it came from. They are meant to be used in addition to standard screening.
How accurate is the Galleri test?
In PATHFINDER 2, about 60 percent of positive results were confirmed as cancer, and false positives occurred in fewer than half a percent of people. However, it detected only about 39 percent of all cancers diagnosed, so a negative result does not rule out cancer.
Did the NHS-Galleri trial show a benefit?
It did not meet its main goal of reducing stage III and IV cancers combined, but it showed fewer stage IV cancers and fewer emergency diagnoses in the tested group. Whether the test reduces deaths is not yet known.
Can these tests detect cancer recurrence?
They are designed for screening people without cancer. After a diagnosis, tumor-informed ctDNA tests are much more sensitive for monitoring recurrence.
About the author. Dr. Silver, MD, graduated from Temple University School of Medicine, trained as an interventional cardiologist, and has practiced medicine for nearly fifty years. A lymphoma survivor of about twenty-five years, he is co-author, with Dr. Lindmeier, DHSc, of The New Reality of Cancer: The Science of Recovery. Read more about Dr. Silver, MD.
Research by Dr. Lindmeier, DHSc, cancer educator and co-author of The New Reality of Cancer.
This article is for general education only and is not individual medical advice. Always consult your own doctor before making any changes to your care.
© 2026 Cancer Expert MD, Dr. Silver, MD, and Dr. Lindmeier, DHSc. All rights reserved. This article draws on the research in The New Reality of Cancer and may not be copied, republished or distributed without written permission.
For more in-depth information on this topic and many others, get our book, The New Reality of Cancer: The Science of Recovery.
More articles on advanced cancer testing and all articles.
References
- Nabavizadeh N, et al. Performance and safety of a multi-cancer early detection test: the PATHFINDER 2 study. Nature Medicine. Published 22 September 2026.
- NHS-Galleri randomized controlled trial: main results. New England Journal of Medicine. Published 22 September 2026.
This article is for education only. It is not medical advice and does not diagnose or treat any condition. Cancer Expert MD has no financial relationship with any laboratory, drug maker, supplement company, clinic or hospital.