A blood test that screens for dozens of cancers is heading to the FDA. Critics say the data isn't there yet.

A patient walks into a primary care office for a routine checkup. The doctor orders a single blood draw. A week later, the result flags a "cancer signal" somewhere in the body, with a guess at where. That sets off a follow-up cascade: imaging, biopsies, specialist visits, and weeks of waiting, all to find out whether the signal is real.

That cascade is what Grail's Galleri test is designed to produce. Galleri is a multi-cancer early-detection (MCED) blood test: it reads cancer-specific methylation patterns from a single tube of blood, screens for a signal shared by more than 50 cancer types, and predicts where in the body that signal is coming from. It is already sold by prescription in the United States as a laboratory-developed test and ran more than 61,000 times in the second quarter of 2026, up 35% from a year earlier (MedTech Dive).

On September 23, 2026, the FDA's Molecular and Clinical Genetics Panel of the Medical Devices Advisory Committee will meet in Silver Spring, Maryland, to discuss, make recommendations, and vote on whether the agency's evidence base supports broader use of Galleri. The panel will not approve or reject the test on the spot. It will advise the agency on whether the current data package meets the bar for a premarket approval application, and on what conditions. The FDA will then weigh that advice before making its own decision.

Grail's premarket application rests on PATHFINDER 2, a US-based study of 25,490 consented participants followed for one year, designed to measure the test's analytical and clinical performance: how often it raises a signal, where, and whether cancer is actually found on follow-up (GRAIL press release). The harder question, and the one critics will press at the meeting, is the one Grail's three-year NHS-Galleri randomized trial in the United Kingdom was built to answer: does catching these signals earlier actually reduce the number of late-stage cancer diagnoses, or the number of cancer deaths?

It did not. NHS-Galleri failed its primary endpoint: there was no statistically significant reduction in late-stage diagnoses across the whole screened population, though Grail reported a favorable trend in a prespecified subgroup of 12 cancers (MedTech Dive). The trial does not yet answer the mortality question, which will take longer to mature. The FDA's advisory panel will weigh a test whose sensitivity and specificity data are strong against a clinical-outcomes study that did not show what the screening category is supposed to show.

Three concrete risks will frame the panel's review. False positives trigger imaging workups, biopsies, and anxiety in patients who do not have cancer. False negatives give false reassurance to patients who do. The test is positioned as a complement to, not a replacement for, guideline-recommended screenings like mammography and colonoscopy, and access today depends on whether a patient can pay out of pocket.

Grail argues the data are enough to support a broader approval now. The company holds a Breakthrough Device designation from 2018, which the FDA uses to fast-track reviews of technologies that could address unmet needs, and submitted its premarket application on January 29, 2026 (GRAIL press release).

A yes vote from the panel would not put Galleri on every clinic's shelf, but it would tell the FDA that the evidence rules for an entire class of multi-cancer screening tests have been met by at least one product in the category. A no vote, or a yes conditioned on a confirmatory trial, would reset the playbook for every MCED developer now waiting in line. Public comments on the meeting close September 16.