Full Breakdown
Galleri Blood Test Shows Promise in Early Cancer Detection
10/21/2025, 10:57:53 AM
Overview of the PATHFINDER 2 Study
GRAIL Inc. recently presented findings from its PATHFINDER 2 study at the European Society for Medical Oncology Congress 2025, demonstrating that the Galleri multi-cancer early detection (MCED) blood test significantly enhances cancer detection rates. The study, which involved 35,878 participants aged 50 and older across the United States and Canada, revealed that when Galleri was added to standard screenings for breast, cervical, colorectal, and lung cancers, the detection rate increased more than sevenfold. Specifically, the test identified cancer signals in 216 participants, leading to 133 confirmed cancer diagnoses, resulting in a positive predictive value of 61.6%.
Key Findings and Efficacy
The Galleri test exhibited a sensitivity of 40.4% for all cancers and 73.7% for the 12 cancers responsible for two-thirds of cancer deaths in the U.S. Notably, 53.5% of the detected cancers were at stages I or II, which are generally more treatable. The test also demonstrated a specificity of 99.6%, with a low false positive rate of 0.4%. Approximately 75% of the cancers identified by Galleri do not currently have standard screening options available.
Diagnostic Resolution and Safety
The Galleri test accurately identified the origin of cancer signals 92% of the time, with a median diagnostic resolution time of 46 days. Only 0.6% of participants underwent invasive procedures during the diagnostic workup, and no serious adverse events were reported. GRAIL plans to submit the PATHFINDER 2 data to the U.S. Food and Drug Administration (FDA) for premarket approval, having already received Breakthrough Device Designation.
Insights from the NHS Study
Complementing the PATHFINDER 2 findings, a study conducted by the University of Oxford involving 6,238 NHS patients indicated that the Galleri test could effectively identify cancers in individuals initially deemed to have false positive results. In this study, 35.4% of those labeled as false positives were later diagnosed with cancer within two years. The Galleri test's ability to pinpoint the cancer's origin was confirmed in nearly all cases, suggesting its potential utility in guiding GPs toward appropriate diagnostic pathways.
Criticism and Cautions
Despite the promising results, experts caution that the Galleri test is not a replacement for standard screenings. Concerns about overdiagnosis and the need for further evidence to establish its impact on mortality rates have been raised. Claire Turnbull, a professor at the Institute of Cancer Research, emphasized the necessity of randomized trials to determine whether early detection via Galleri reduces cancer mortality.
Conclusion and Future Directions
The Galleri test represents a significant advancement in cancer detection, particularly for cancers lacking routine screening options. With ongoing studies, including a large-scale NHS trial involving 140,000 patients, the future of Galleri in clinical practice remains to be seen. Sir Harpal Kumar, president of GRAIL, highlighted the test's potential to transform cancer diagnostics, advocating for its integration into existing healthcare frameworks to facilitate earlier and more effective treatment interventions.
Verbatim Quotes
- “These results are extremely compelling as approximately three-quarters of the Galleri-detected cancers do not have recommended screening tests today.” — Josh Ofman, MD, MSHS, President at GRAIL
- “This robust data demonstrates the potential benefit of the Galleri test as a diagnostic tool for individuals presenting with symptoms of cancer, particularly where those symptoms are non-specific.” — Sir Harpal Kumar, President of International Business and BioPharma at GRAIL
- “To put that into context, we currently refer people for urgent investigation and only 6% of them are diagnosed with cancer, so to have a test that could possibly get you up to 84%, we would argue, would be a very valuable addition and enable much more efficient diagnostic investigation.” — Sir Harpal Kumar
What's Next
GRAIL anticipates completing its modular premarket approval submission for the Galleri test in the first half of 2026, while results from the NHS trial are expected to provide further insights into the test's efficacy and potential integration into routine cancer screening practices.
