FDA advisers backed a multi-cancer blood test. The vote on whether it works was 6-4.

What the panel voted on. The FDA’s Molecular and Clinical Genetics Panel met on September 23 to review GRAIL’s premarket approval application. The proposed use is screening for multiple cancer types in adults aged 50 or older. The ten voting members voted 10-0 on safety, 6-4 on effectiveness, and 7-2 with one abstention that the benefits outweigh the risks. The FDA does not have to follow a panel. It often does.

Four of ten advisers were not convinced it works. Unanimous on safety makes sense: the test is a blood draw. The effectiveness vote is where the doubt sits. NBC News reported the panel raised concerns about false assurance and false alarms even as it voted yes. Two sets of data explain the split.

A positive result means something. GRAIL presented PATHFINDER 2 at ASCO in May: 35,878 people aged 50 and up with no suspected cancer. Specificity was 99.6%, so fewer than 4 in 1,000 cancer-free people got a false positive. Of those who tested positive, 60.3% were diagnosed with cancer, and the test named the likely organ of origin correctly 91.3% of the time. These are conference results reported by the company, not yet a peer-reviewed paper.

A negative result means less. The same PATHFINDER 2 data put episode sensitivity at 39.3% across all cancers. Of the cancers that turned up in participants during the study window, the test flagged about four in ten. For the 12 cancers GRAIL says cause most cancer deaths, it flagged 69.8%. Most cancers it did catch were early: 53.0% at stage I or II. A clean Galleri result lowers the odds you have one of those cancers. It does not rule one out.

The trial that would settle it has not settled it. The NHS-Galleri trial randomized 142,250 people aged 50 to 77 in England to three annual tests or usual care. Its primary goal was fewer stage III and IV cancers. It missed: the incidence rate ratio was 1.03 (p = 0.63). Stage IV diagnoses fell 14% overall, and 22% and 26% in the second and third rounds, in secondary analyses. No mortality data yet. Ajay Goel of City of Hope told Scientific American: “We still need longer term evidence showing that this leads to fewer advanced cancers.”

You could already buy it. GRAIL made Galleri available by prescription in June 2021 as a laboratory-developed test, validated by GRAIL’s own CLIA lab rather than cleared by the FDA. The list price is $949. Approval would add FDA review of the performance claims and could shift how insurers treat it. It would not change what a result can and cannot tell you.

What to do with this. Both big studies added Galleri to standard screening. If you are 50 or older and considering it, keep your colonoscopy, mammogram, cervical screening and, if you qualify, low-dose lung CT on schedule. Treat a positive as a reason for prompt imaging and a specialist visit; about four in ten positives in PATHFINDER 2 were not cancer. Treat a negative as partial information. Nothing on a routine blood panel measures what Galleri measures, so a normal CBC or metabolic panel says nothing either way about cancer DNA in your blood.