Multicancer blood test detects cancer signals across 17 tumor types

A prospective study found that a multicancer early detection blood test identified cancer signals across 17 broad cancer types, including ovarian, lung, breast and colorectal cancers, as well as several cancers for which routine screening is not recommended. Published in Nature Medicine, the PATHFINDER 2 study evaluated the test in adults aged 50 and older and measured how often positive results were followed by a cancer diagnosis, how accurately the test identified likely cancer origins and how many cancers were detected at relatively early stages.

The study enrolled 35,878 adults and included 32,007 participants in its performance analysis. Among them, 287 received a positive result from the multicancer early detection test, or MCED test. A cancer was subsequently diagnosed in 173 of those participants, corresponding to a positive predictive value of 60.3%. The test’s specificity was 99.64%. When a participant had a true-positive result, the test correctly predicted one of the two most likely origins of the cancer signal in 91.3% of cases. These results describe the test’s performance in the studied population; they do not establish that it reduces cancer mortality or improves clinical outcomes compared with standard screening.

The MCED test analyzes small DNA fragments released by cells into the bloodstream. Researchers examine patterns in those fragments for signals associated with cancer. If the analysis detects a cancer signal, the test also estimates one of the most likely locations of the cancer to help guide additional diagnostic testing. In PATHFINDER 2, 72.8% of the cancers detected through the test were in cancer types without U.S. Preventive Services Task Force grade A or B screening recommendations. The investigators described this as a potential means of identifying cancers that might otherwise be missed during routine screening, while emphasizing that MCED testing is not a replacement for established screening programs.

Stage information was available for 151 participants with at least one newly diagnosed primary cancer detected by the test. Of these cancers, 53% were stage 1 or stage 2, while 70.9% were stage 1, stage 2 or stage 3. The findings suggest that the test can identify a substantial share of cancers before the most advanced stages, but the single-arm design prevents direct comparison with standard screening or no screening. The researchers said randomized trials and longer follow-up are needed to determine whether MCED testing has clinical utility in routine practice. The study also evaluated an earlier version of the test that has since been replaced by a commercially available version.

PATHFINDER 2 was designed and funded by GRAIL Inc., which also participated in data analysis and interpretation and in preparing the manuscript. Mayo Clinic was one of the participating institutions; medical oncologist Karthik Giridhar was an investigator and senior author. Giridhar disclosed consulting and advisory relationships with GRAIL and other organizations, as well as travel expenses from GRAIL. Because the study was interventional but had no comparator group and used descriptive endpoints without formal hypothesis testing, its numbers primarily characterize detection performance rather than proving benefit from screening. Its high specificity and broad coverage of cancers without established screening recommendations may be notable, but the positive predictive value also means that a positive result did not lead to a cancer diagnosis for every participant.

Subject of Research: Prospective evaluation of a multicancer early detection blood test in adults aged 50 and older

Article Title: Multicancer blood test detects 17 cancer types in large prospective study

Article References: Multicancer blood test detects 17 cancer types in large prospective study. Original publication (Bibliographic details unavailable.)

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Keywords: multicancer blood test, MCED testing, PATHFINDER 2, liquid biopsy, cancer screening, early detection, ctDNA, Nature Medicine, prospective study, Multicancer, blood, test