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Medical Daily

A Blood Test for 50 Cancers Goes Before the FDA: An Oncologist Explains What the Evidence Really Shows

St Cancer FDA Galleri Grail NHS

^{Editorial Note: This article is an internal production sample used exclusively for contributor outreach. All content, author bios, and associated data are strictly illustrative and fictional.}

Most of the cancers that kill Americans have no routine screening test. We can screen for breast, colorectal, cervical, and, in high-risk smokers, lung cancer. Pancreatic, ovarian, liver, and esophageal cancers are usually found only after symptoms appear, and by then they have often spread.

That gap is why multi-cancer early detection (MCED) blood tests have drawn so much attention, and why this week matters. On September 23, 2026, an FDA advisory committee is meeting in open session to discuss and vote on the premarket approval application for the Galleri test from GRAIL, Inc. No blood test that screens for multiple cancers has yet passed the FDA's safety and accuracy review.

As an oncologist, I see patients every week whose cancer was found too late to cure. I also see what happens when a screening test sends a healthy person through months of scans and biopsies. Both realities shape how I read the Galleri data.

How the Galleri Test Works

When cells die, they release small fragments of DNA into the bloodstream. Cancer cells leave a distinctive chemical fingerprint on that DNA through a process called methylation, which works like a set of on-off switches for genes. Galleri is a prescription-only test that uses next-generation sequencing to look for cancer-specific methylation patterns in this cell-free DNA, and it also predicts where in the body a detected cancer signal most likely started.

The test is not new to the market. GRAIL began selling Galleri as a laboratory-developed test in 2021, a pathway that does not require FDA approval. It currently costs $949 out of pocket.

What the Largest Trial Found

The strongest evidence comes from England. The NHS-Galleri trial is the first randomized, controlled trial of any MCED test, and it evaluated annual Galleri screening over three years in 142,250 adults aged 50 to 77. Half of participants received the blood test on top of the usual national screening programs, and half received usual screening alone.

Some findings were encouraging. In the test group, stage 4 diagnoses fell 9% in the first screening round, 22% in the second and 26% in the third, for an overall 14% reduction across 12 prespecified deadly cancers. Stage 1 and 2 diagnoses of those cancers rose 16%, with large increases in cancers usually caught late, including ovarian, esophageal, pancreatic and liver cancers. Adding the blood test also produced a four-fold increase in screen-detected cancers and a 25% drop in cancers diagnosed after an emergency presentation.

The test's accuracy held up in a real-world population. Over three rounds, 1,801 participants (0.91%) got a positive result, and 937 were diagnosed with cancer, for a positive predictive value of 52%. Specificity was 99.55%, and the test correctly predicted the cancer's location 92.5% of the time.

The Result That Did Not Go as Planned

The trial's primary goal was different. Researchers wanted to show a drop in stage 3 and stage 4 cancers combined. That combined reduction was not statistically significant within one year of follow-up after the last screening.

GRAIL's explanation is that the first round of testing uncovered a large number of stage 3 cancers already present in the population. The company says the drop in stage 4 cases was outweighed by a rise in stage 3 cases, particularly in the first round, and that it expects more undiagnosed late-stage cancers to surface in the control group with longer follow-up. That is a plausible argument, but it is still a hypothesis.

Independent experts have urged caution. In an editorial in BJC Reports, Nitzan Rosenfeld of the Barts Cancer Institute praised the trial's rigor but called the missed endpoint disappointing and warned that reading results in hindsight risks "moving the goal posts," noting that the results shared so far appear to highlight the more favorable findings. He also pointed out that the trend toward fewer late-stage cancers in later rounds raises the possibility that the benefit grows with continued screening, but that this remains untested.

What the Research Does, and Does Not, Show

This is where a clinician's perspective matters most. The trial measured stage shift, meaning whether cancers were found at earlier stages. It did not measure whether fewer people died of cancer, which is the outcome patients care about most.

Those two things are not the same. Finding a cancer earlier can look like a survival gain even if it changes nothing, a problem researchers call lead-time bias. Rosenfeld notes that earlier-stage survival reflects partly real cure and partly this lead-time effect, that the two are hard to separate, and that this is a key weakness of stage-shift endpoints. Screening can also find slow-growing cancers that would never have caused harm, which leads to treatment people did not need.

Sensitivity is the second issue. The test detected 54.7% of the 12 prespecified cancer types diagnosed within 12 months of a blood draw, and 30.7% across all cancer types. In plain terms, a negative result misses many cancers. Rosenfeld warns that people with negative results may be falsely reassured and that current screening must continue alongside the test.

False positives are relatively uncommon but real. After three annual rounds, about 1.2% of people in the test group were sent for workups that did not find cancer, which can mean CT or PET scans, procedures, costs and considerable anxiety.

Two further caveats deserve attention. The full NHS-Galleri results have not yet been published in a peer-reviewed journal. And the version under FDA review is not identical to the one tested in England. GRAIL's application includes an analysis comparing the version used in its trials to an updated version submitted for approval.

What Oncologists Want Patients To Know

First, a multi-cancer blood test is an add-on, not a substitute. GRAIL itself says Galleri should supplement standard screenings like colonoscopies and mammograms, not replace them. Skipping a colonoscopy because a blood test came back negative would be a serious mistake.

Second, a negative result does not mean you are cancer-free. New symptoms such as unexplained weight loss, persistent pain, bleeding or a lump still need prompt medical attention, whatever a blood test said months ago.

Third, a positive result is the start of a process, not a diagnosis. Roughly half of people with a positive result in the trial had cancer, and the other half did not. Anyone considering the test should ask their doctor ahead of time what follow-up would look like and whether their insurance would cover it.

Finally, these tests are designed for people at higher risk, mainly adults 50 and older. They are not meant for young, healthy adults looking for general reassurance.

What Happens Next

The advisory panel's vote is not the final word. The recommendation is not binding, though the FDA generally follows its advisory committees. The agency asked the panel to weigh whether the data show the test detects cancers reliably and early enough to support such claims in its marketing, as well as the harms of false results.

Approval would carry real consequences for access. A law signed on February 3, 2026, allows Medicare, beginning in 2028, to cover FDA-approved multi-cancer screening tests if the Centers for Medicare & Medicaid Services determines coverage is appropriate.

The mortality question is being studied separately. The National Cancer Institute's Vanguard Study will enroll up to 24,000 people to help design a much larger randomized trial that will test whether multi-cancer tests reduce cancer deaths and whether their benefits outweigh their harms. Follow-up in NHS-Galleri also continues, and longer-term data may show whether the drop in stage 4 cancers grows over time.

The Bottom Line

The NHS-Galleri trial shows that a single blood draw can detect many cancers, including some with no current screening option, and that annual testing reduced stage 4 diagnoses. It did not meet its main goal, and no study has yet shown that the test helps people live longer.

For now, the evidence supports cautious interest, not enthusiasm. Patients who are curious should talk it through with a doctor, understand what a positive or negative result can and cannot mean, and keep up with every recommended screening test they already have.

About the Author

Jane Sample, MD

Jane Sample, MD, is a board-certified medical oncologist at Example Regional Cancer Center in Anytown, ST, where she treats patients with a range of solid tumors and has a clinical interest in cancer screening and early detection. She completed her hematology and oncology fellowship at Example University Medical Center and Associate Professor of Medicine at Example State University School of Medicine. Her work focuses on evaluating new cancer screening technologies in primary care populations.

Contact: Division of Medical Oncology, Example Regional Cancer Center, 100 Sample Street, Anytown, ST 00001 | [email protected] | (555) 010-0101

Disclosures: Dr. Sample reports no financial relationships with GRAIL, Inc. or other developers of multi-cancer early detection tests.