Grail's Galleri Blood Test Fails to Reduce Late-Stage Cancers in Major Trial

A blood test aimed at early detection of cancer failed to reduce late-stage cancers in a major clinical trial, the test's maker, Grail, announced. The study, known as the NHS-Galleri trial, found no statistically significant reduction in late-stage cancer diagnoses among participants screened with Galleri, raising questions about whether multi-cancer early detection blood tests can deliver meaningful patient outcomes.

Grail's test, known as Galleri, looks for minuscule shards of cancer DNA in the blood for more than 50 types of cancer. It has been sold in the United States since 2021 and costs $949. Even though it is not yet approved by the Food and Drug Administration, the company sells it under a regulatory loophole that permits sales of certain tests without review. Very few insurers cover the test, so most people pay for it out of pocket. Grail has sold nearly half a million of the tests so far, including more than 185,000 last year. In February 2026, a Super Bowl advertisement by Hims & Hers promoted the test.

The company lobbied heavily for the U.S. government to cover the test under Medicare. The spending package passed by Congress and signed into law by President Trump earlier this month authorized Medicare to cover cancer detection tests, and Galleri could be among those that qualify to receive the government's approval. Grail, which has its headquarters in Silicon Valley, plans to present more detailed results from the study at a cancer conference in the spring.

Galleri has shown promise in earlier studies. In the PATHFINDER 2 study, which enrolled over 35,000 adults aged 50 and older, adding Galleri to standard US-recommended screenings increased cancer detection more than seven-fold, with over half of the newly detected cancers found at early stages. The test also correctly predicted the tumor's location in 92 percent of cases. However, early findings from the NHS-Galleri trial suggest that earlier detection did not produce a measurable shift in the overall stage at diagnosis, a crucial benchmark for understanding a test's potential impact on patient outcomes.

The trade-offs of breadth versus depth are central to the field. While Galleri has demonstrated an ability to detect a broad range of cancers, multi-cancer early detection tests face biological, technical, and healthcare-system challenges. In asymptomatic populations, these tests rely on detecting tumor-derived biomarkers circulating in the blood. However, tumors vary widely in how much DNA they shed, and some cancers may release detectable fragments only once the disease has progressed. Expanding a single assay to cover dozens of cancer types can also dilute sensitivity for any individual cancer, increasing the risk of missed early-stage disease. Even with high specificity, false positives can generate unnecessary anxiety, diagnostic procedures, and healthcare costs.

According to a chief medical officer at Michigan Institute of Urology, "While there were encouraging signals, it did not show a clear reduction in late-stage cancers. The technology is promising, but we're not yet at the point where it can serve as a population-wide screening solution." A pharmaceutical sciences researcher at Texas A&M University noted that "although the clinical reliability of blood tests is improving, one of the reasons liquid biopsy tests are not yet used as standalone diagnostics is their sensitivity limitations across cancers and stages, especially for early-stage cancers, which restrict their use as independent diagnostic tests."

By contrast, a more focused approach allows for fine-tuning to maximize both sensitivity and specificity. Targeted tests can be calibrated to detect subtle biological signals unique to that cancer. The FDA recently approved Freenome's SimpleScreen CRC blood test, the second blood-based test for colorectal cancer screening. In clinical studies, the test detected roughly 8 in 10 colorectal cancers. The test detects patterns of cytosine-phosphate-guanine (CpG) methylation, changes that often occur early in cancer development. Results are generally available within approximately two weeks, and a positive result requires a follow-up colonoscopy.

Although blood tests are considered better than no screening, the American Gastroenterological Association and the American Society for Gastrointestinal Endoscopy conclude that current blood-based tests are less effective than established screening options and should generally be reserved for individuals who are otherwise unwilling to undergo recommended screening with colonoscopy or stool-based tests. Blood-based testing may help to improve screening uptake, particularly among those who are unscreened or overdue for screening.

In another focused application, researchers at the Cancer Research UK National Biomarker Centre have developed a liquid biopsy test powered by AI for Ewing sarcoma, a rare bone and soft tissue cancer that predominantly affects children and adolescents. The test uses a machine learning model called EwingSign to identify patterns in DNA fragments rather than single mutations. In a study examining blood samples from 26 children and young adults with Ewing sarcoma, the test detected signs of cancer in 15 of the 18 patients whose disease had already returned. The study lead said it is the first liquid biopsy development for children's cancers from the center, and larger studies will be needed to determine whether the model can fulfill its promise.