Trial reports how a blood test detected cancer signals in adults aged 50 and older
The PATHFINDER 2 study assessed test accuracy and the safety of follow-up procedures, but did not establish whether testing improves survival or other health outcomes.
Moderate evidenceHuman studyInterpret with caution
Medical disclaimer: This article summarizes research findings and is for informational purposes only. It is not medical advice.
Editorial illustration — not from the study.
The prospective PATHFINDER 2 clinical study enrolled 35,878 adults aged 50 and older between December 2021 and July 2024. The researchers assessed how often the test detected cancer signals, how accurately it identified the likely cancer location, and what happened during diagnostic follow-up over 12 months.
Among 32,007 participants included in the performance analysis, the test had 99.64% specificity, meaning most people without a detected cancer did not receive a positive result. The study reported that 213 of 35,335 safety-analyzable participants, or 0.6%, underwent invasive procedures after a positive test; 90.5% of these procedures were nonsurgical. The abstract reports no serious study-related adverse events by the time of analysis, but randomized trials and longer follow-up are needed to assess clinical usefulness.
The question examined
This human clinical trial examined the performance and safety of a blood-based multi-cancer early detection test. The test was designed to detect a cancer-related signal and predict its likely signal origin to help guide diagnostic evaluation. The study enrolled 35,878 adults aged 50 or older who had no clinical suspicion of cancer. Performance was analyzed in 32,007 participants, and safety was analyzed in 35,335 participants, with safety follow-up lasting 12 months. The endpoints were analyzed descriptively, and no hypothesis testing was performed.
What the study found
In the performance-analyzable group, the cancer detection rate was 0.54% (95% confidence interval, 0.47%–0.63%). The positive predictive value was 60.3%, meaning that about 60% of positive test results were associated with a confirmed cancer in this study. The negative predictive value was 99.2%, and specificity was 99.64%. The test detected 39.3% of all cancer episodes and 69.8% of cancer episodes in a prespecified 12-cancer subgroup. Its prediction of the likely cancer location was accurate in 91.3% of cases. Among safety-analyzable participants, 0.6% had invasive procedures after a positive test, with most of those procedures being nonsurgical. No serious study-related adverse events had been reported by the time of this analysis.
Who this is relevant to
These findings may apply most closely to adults aged 50 and older without a clinical suspicion of cancer who are similar to the participants enrolled in this study and who use this specific test. They should not automatically be applied to younger people, people with symptoms or a known cancer risk, other tests, or other health-care settings. The study does not establish whether testing benefits patients or should replace any established screening approach.
The significance
The findings provide information about how this particular blood test performed in an intended-use population and about the invasive procedures that followed positive results. They do not show that using the test reduces deaths, improves survival, or provides a net health benefit. A positive result can lead to additional diagnostic procedures, so test accuracy alone does not establish the overall value of screening.
Limitations & evidence assessment
The study was not described as randomized, and the abstract does not report a comparison group. Results were analyzed descriptively without hypothesis testing. Follow-up for safety was 12 months, while the longer-term effects of screening, including whether it changes cancer outcomes, remain unknown. The abstract also provides limited information about how participants were selected, how cancers were confirmed, and the full range of diagnostic harms. The researchers explicitly state that randomized trials and longer follow-up are needed to assess the clinical utility of multi-cancer early detection tests.
Why this evidence level: This was a large prospective interventional study in people, with more than 35,000 participants, but the results were analyzed descriptively without hypothesis testing. Randomized trials and longer follow-up are still needed to determine whether this testing improves health outcomes.
Evidence levels are editorial estimates derived from study metadata — they are not clinical appraisals.
// Source
Nature Medicine · 2026 · DOI: 10.1038/s41591-026-04618-w
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