Early detection: the blood test debate
What a multi-cancer blood test can and cannot do, the trials that will decide, and the statistics you need to judge the claims.
- 1FrontEarly Detection & Screening
Early detection and screening means finding cancer before it causes symptoms, when it is most curable.
Why here The front and what screening has already achieved.
- 2TechnologyPhase 3Multi-cancer early detection (MCED)
A single blood test intended to screen for dozens of cancers at once, including ones with no screening today.
Why here The technology, its promise, and its open questions.
- 3ProductPhase 3Galleri
A blood test screening for more than 50 cancers at once, before the FDA in September 2026.
Why here The test in front of the FDA in September 2026.
- 4TermPositive predictive value (PPV)
Positive predictive value (PPV) is the chance that a test saying 'cancer' is right.
Why here The number that decides how many false alarms a positive test causes.
- 5TermStage shift
Stage shift means finding more cancers early and fewer late; it is the measurable goal of screening.
Why here The endpoint the NHS trial measures, and why it is not the same as saving lives.
- 6TrialCompletedNHS-Galleri
The largest cancer screening trial ever run, testing whether a multi-cancer blood test reduces late-stage diagnoses.
Why here The largest cancer screening trial ever run.
- 7TrialCompletedPATHFINDER 2
PATHFINDER 2 is the US real-world study of the Galleri test that forms the core of its FDA submission.
Why here The US real-world study behind the FDA submission.
- 8ProductApprovedShield
The first FDA-approved blood test for colorectal cancer screening (2024), now optionally reporting other cancers too.
Why here The blood test already approved for one cancer.
- 9IdeaFAPI PET as the workup for MCED positives
When a blood test says 'cancer signal, origin unclear', a FAPI PET scan may find it where FDG cannot.
Why here A proposal for what to do after a positive result.
- 10RoadmapEarly detection roadmap: organ screening → blood tests for many cancers
From mammograms and colonoscopies to a single blood draw that might screen for dozens of cancers, with the FDA's first decision imminent.
Why here The path from Pap smears to a single annual draw.