A groundbreaking blood test capable of detecting over 50 types of cancer has shown promising results in a large screening trial. The PATHFINDER 2 study of the Galleri multi-cancer early detection (MCED) test demonstrated a significant increase in cancer detection rates when combined with standard screenings.
Key Discoveries in Cancer Screening
Results unveiled at the European Societyopean Society for Medical Oncology Congress 2025 in Berlin indicated that more than half of the cancers detected were in early stages (stage I or II), which are more treatable. The majority of these cancers, such as pancreatic, liver, ovarian, and stomach cancers, do not currently have standard screening protocols.
Dr. Josh Ofman, President of GRAIL, Inc., emphasized the importance of early detection: “Cancer is the second leading cause of death worldwide as most deadly cancers are found too late. Adding Galleri to recommended screening yielded a more than seven-fold increase in the cancer detection rate, and more than half of the Galleri-detected new cancers were found in early stages, when cancers are more treatable and potentially even curable.”
Implementation in the National Health Service
The UK’s National Health Service is conducting a large-scale trial of the Galleri test, aiming to enroll over 140,000 participants. Initial results are anticipated next year, with the objective of evaluating the impact of MCED screening on cancer outcomes at a population level.
If successful, the NHS plans to extend the test to an additional one million individuals, potentially establishing the first national MCED screening initiative globally.
Sir Harpal Kumar, President of Biopharma at GRAIL, highlighted the significance of early detection: “The vast majority of people who die from cancer do so because we find their cancers too late. The aim is to shift to earlier detection, when we have the chance to use treatments that are much more effective and potentially curative.”
This initiative is crucial in the UK, where many cancers are typically diagnosed at advanced stages. By integrating Galleri into existing screening programs, the NHS aims to bridge the gap between detection and treatment for cancers like ovarian, pancreatic, and stomach.
Impact on Public Health
Current cancer screening programs focus on a limited number of cancer types. According to the U.S. Preventive Services Task Force, the majority of cancer deaths are attributed to cancers without standard screening methods. A single blood test capable of detecting multiple cancers early could revolutionize cancer care, leading to improved outcomes, reduced costs, and enhanced health equity.
Dr. Nima Nabavizadeh of Oregon Health & Science University, a co-leader of the PATHFINDER 2 study, emphasized the potential of Galleri: “Galleri could fundamentally change our approach to cancer screening, helping to detect many types of cancer earlier, when the chance of successful treatment or even cure are the greatest.”
Early detection at a population level could alleviate the financial burden of late-stage cancer treatment. Cancer care is a significant expense in healthcare, with late-stage treatments costing substantially more than early interventions. Early detection could lead to better outcomes and reduced costs across the healthcare system.
Functionality of the Test and its Significance
Unlike traditional tests, Galleri does not target a single cancer type. It analyzes cell-free DNA fragments released by tumors into the bloodstream, identifying methylation patterns that indicate the presence of cancer.
The specificity of Galleri is 99.6%, with a low false positive rate of 0.4%. Its positive predictive value (PPV) is around 62%, meaning that the majority of positive results correspond to actual cancer cases.
Equally important is Galleri’s ability to identify the origin of the cancer signal within the body. In the PATHFINDER 2 study, Galleri accurately determined the cancer’s origin in 92% of cases, enabling targeted diagnostic procedures and minimizing unnecessary interventions. Only a small percentage of participants required invasive procedures, and no serious adverse events were reported.
As Dr. Ofman explained, “Any multi-cancer early detection test used for population screening should aim to detect as many aggressive cancers as possible before symptoms arise and maximize the likelihood that a positive test result is actually cancer. Galleri is doing just that.”
The Grail Journey: A Decade in the Making
The origins of Grail trace back to a serendipitous discovery at Illumina, Inc. in 2015, where non-invasive prenatal tests unexpectedly detected cancer DNA signals in pregnant women. This revelation led to the establishment of Grail in 2016, with a mission to develop a revolutionary early cancer detection test.
Since then, Grail has garnered funding, advanced its methylation-based platform, and introduced the world’s first commercial MCED test, Galleri, in 2021. Its evolution reflects the trajectory of modern precision medicine, leveraging genomic insights, machine learning, and large-scale trials to reshape public health.
Future Prospects
While the results of Galleri are promising, the true measure of success lies in reducing cancer-related deaths. Professor Clare Turnbull of The Institute of Cancer Research emphasized the need for randomized studies with mortality as an endpoint to validate the benefits of early detection by Galleri.
Nevertheless, with trials in the US and UK progressing towards regulatory approval and potential widespread adoption, Galleri could become the first widely used MCED screening test. If successful, it has the potential to revolutionize cancer care by shifting the focus from late-stage treatment to early-stage prevention.
