Early-Detection Tests and Multi-Cancer Screening Research

What the large studies found

NHS-Galleri (England, randomized). The trial randomized 142,250 people aged 50 to 77 to be offered the test or to receive usual care. [5] It did not meet its primary endpoint of reducing the combined number of stage III and IV cancers. [5] Fewer stage IV cancers were seen in the test group, which was a pre-specified secondary outcome, and more stage I and II cancers were diagnosed. [5] The researchers said longer follow-up is needed to see how these differences develop. [5] The trial was funded by GRAIL, the test's maker. [5]

NHS-Galleri test performance. Across three yearly rounds, specificity ranged from 99.50% to 99.60%, and the share of positive results that were confirmed as cancer (positive predictive value) fell from 58.0% to 50.4% to 45.8%. [6] Episode sensitivity, meaning the share of cancers diagnosed in the following year that the test caught, ranged from 26.7% to 37.2% for all cancers. [6] These performance results were descriptive, without hypothesis testing. [6]

PATHFINDER 2 (North America, prospective interventional study). Among 35,878 enrolled people aged 50 or older, positive predictive value was 60.3% and episode sensitivity was 39.3% for all cancers. [7] After a positive test, 213 people (0.6% of the safety group) had invasive procedures. [7] The authors state that randomized trials and longer follow-up are needed to assess clinical utility, and some authors are GRAIL employees. [7]

Independent review. A 2025 systematic review for the UK's NIHR found no completed randomized trials at the time and a high risk of bias in most studies. [3] It found that sensitivity was highly variable and lower for earlier-stage (I-II) than later-stage (III-IV) cancers. [3]

What the FDA panel said

The panel agreed the test's value is greatest for cancers without guideline-recommended screening, and that it should not replace established, guideline-recommended screening. [4] Panelists saw substantial variability in sensitivity across cancer types. [4] They generally doubted that the word "early" in the intended use was supported, noting the test generally did not detect stage I cancers as often as stages II to IV. [4] They also said the long-term impact on patient outcomes has not been established, and that a positive result does not confirm cancer while a negative one does not rule it out. [4]

Why "finds cancer" is not the same as "helps"

• Sensitivity is limited. Most cancers present in the following year were not flagged in either large study. [6][7]
• False alarms are uncommon but real. Even at about 99.5% specificity, screening many people means some will be told of a possible cancer that is not found, with follow-up tests. Fewer than 1 in 200 tests were false positives in NHS-Galleri. [5]
• Earlier is not always better. Finding more early-stage cancers does not by itself show fewer deaths; that is why mortality or late-stage outcomes with longer follow-up matter. [5] See overdiagnosis and screening vs diagnosis.
• A single test result cannot stand in for proven screening. The FDA's questions to the panel named breast, colorectal, lung, cervical and prostate cancer as having current guideline-recommended screening, and the panel recommended labeling stress the need to continue all guideline-recommended screening. [4]

Who should talk with a clinician first

Anyone with symptoms, a past cancer, or a strong family history needs diagnostic care, not a screening test. If a test is offered to you, ask which exact test it is, what its approval status is in your country, what the follow-up plan is after a positive result, and who pays. This page does not recommend or discourage testing for any individual. For related reading, see liquid biopsy research, false positives, multiple testing and incidental findings and talking with a health professional.