Transforming Cancer Screening: The Potential of the Galleri Blood Test

A single ctDNA blood test now demonstrates multi-cancer detection capability with a high specificity and a majority of detections at stage I–II, expanding early-stage identification beyond current single-organ screens. This was determined by the Pathfinder 2 trial, which found that the Galleri blood test detects a cancer signal with a positive predictive value of about 61.6% and very high specificity in a large asymptomatic cohort.

A 61.6% positive predictive value means that a detected cancer signal confers a substantially elevated probability of underlying malignancy and that most detected cases are identified at early stages, though sensitivity varies by tumor type and remains limited for some cancers.

The study also shows that adding the test to existing screening programs yields a large increase in cancers found within the first year. Integration therefore requires structured confirmatory pathways and clear clinician communication to translate positive signals into efficient diagnostic workups while minimizing unnecessary procedures.