Grail’s Galleri multicancer detection test scans a single blood draw for tumor-derived DNA fragments that share a cancer signal and then predicts the likely organ of origin. Investigators reported that a positive result mandates follow-up testing such as imaging or biopsy to confirm cancer. An FDA advisory committee recently voted 6-4 endorsing the evidence of effectiveness presented to the agency. Grail positions the test as additive to guideline-recommended single-cancer screens and intends it for people aged 50 and older. The company has publicly noted commercial uptake, reporting more than 595,000 tests sold through June 30, 2026. A new law could enable Medicare coverage beginning in 2028, and the test currently lists for $949.
Investigators presented several core performance numbers from PATHFINDER 2 and the U.K. NHS-Galleri trial. Specificity was very high in PATHFINDER 2 — reported as 99.6% with a false-alarm rate of about 1 in 280 people without cancer. Positive predictive value (PPV) figures were described in two sources: just over 50% in NHS-Galleri and roughly 62% in PATHFINDER 2. Episode sensitivity, however, remains modest; clinicians cited a range near 30% to 40% in trials capped at 12 months, which implies many cancers are still missed by a single screening episode.
The NHS-Galleri randomized trial was designed to test whether multicancer screening could reduce the incidence of late-stage (Stage 3 and 4) cancers after three annual screening rounds. The study did not meet its primary endpoint, although investigators observed a non-significant trend toward fewer late-stage cancers in the screened group. Those results framed expert caution: high specificity reduces the number of false positives, but limited sensitivity and the negative-test false reassurance risk are pressing concerns.
Expert commentary and reported trial data converge on a clear pattern: Galleri performs best for aggressive, DNA-shedding tumors and less well for slow-growing cancers. Investigators noted strong detection rates for liver and bile duct cancers, colorectal cancers, pancreatic and gallbladder cancers, head and neck cancers, and lymphomas — with cited detection in the range of roughly 75% to 90% for many of those diagnosed within a year in the PATHFINDER 2 cohort. The test also predicted the anatomic origin correctly more than 90% of the time when positive, which helped focus subsequent diagnostic imaging.
By contrast, clinicians emphasized that the test detects far fewer prostate and breast cancers — figures reported were fewer than 1 in 10 prostate cancers and fewer than 1 in 4 breast cancers in trial data. Investigators stressed that existing single-cancer screens such as mammography, colonoscopy and Pap smears retain high sensitivity and must not be displaced by a negative multicancer blood test.
When the test was positive, study teams reported that most follow-up was limited to scans and blood work because the assay usually identified where to look. In PATHFINDER 2 the predicted location was correct over 90% of the time. That accuracy reduced the need for invasive diagnostics: only 0.6% of everyone tested underwent an invasive procedure after a positive Galleri result. The low overall positive rate in trials—about 0.9% of those tested—also tempered concerns about overwhelming primary care workloads with false positives.
Still, clinicians voiced practical worries: positive results require a clear, evidence-based diagnostic pathway to avoid unnecessary tests, patient anxiety, and potential overdiagnosis. Some specialists compared the test’s role to PSA screening of the prostate — a signal, not a diagnosis — and urged clear criteria for when to order the test and how to document and act on positive findings.
Grail has commercially sold hundreds of thousands of tests, and clinicians expect adoption to accelerate if FDA approval is granted. The list price is $949, and broad clinical uptake will depend on payers. A law opening the door to Medicare coverage in 2028 was cited as a potential inflection point, but experts said insurers will want stronger evidence tying earlier detection to improved mortality or patient outcomes before offering routine coverage. Investigators also highlighted that the test’s relative cost compares in some scenarios with other diagnostic procedures, but financing and downstream workup costs could change the economic calculus.
Several specific uncertainties remain. NHS-Galleri did not meet its prespecified primary endpoint of reducing late-stage cancers after three annual screens, and long-term mortality data are not yet available. The trial designs and endpoints have drawn critique from some clinicians, and investigators warned that improvements between PATHFINDER 1 and PATHFINDER 2 reflect iterative science rather than final proof. Experts repeatedly noted the risk of false reassurance from a negative test and the need to preserve guideline-recommended single-cancer screening.
Other unanswered items documented by study teams include the optimal target population beyond the age cutoff, long-term outcomes tied to earlier detection, how to integrate these tests into primary-care workflows, and the implications of a positive result that yields no identifiable tumor on workup. These are the concrete evidence gaps reviewers and clinicians identified as next priorities for research and policy decisions.