Question 228 of 433
What have the Galleri trials actually shown?
The short answer
A low false-alarm rate, good accuracy when it is positive, and modest sensitivity. It finds roughly one cancer in three overall and misses most of the earliest ones. Its largest trial did not meet its main goal.
Here are the numbers a patient needs:
False positives are rare: fewer than one in 200 people tested.
When the test is positive, roughly half to about six in ten people turn out to have cancer, depending on the study.
When cancer is present, the test detects it about a third of the time across all stages. For stage I cancers, the stage where cure is most likely, earlier studies found it detected only about one in six.
The big trial: England’s National Health Service randomized about 142,000 adults. Results were presented in June 2026. The trial did not significantly reduce the combined number of stage III and IV cancers, which was its primary goal. It did show a 14 percent drop in stage IV diagnoses, growing larger in later years of testing, and more cancers found at stages I and II.
Whether it saves lives is not yet known.
“This book is for education. It is not medical advice, and reading it does not make you my patient or create a doctor-patient relationship.” From the book’s medical disclaimer. Full disclaimer
HUMAN SCREENING TRIAL — Adults aged 50–77: stage outcomes and test performance; primary endpoint not met, mortality benefit unproven.Evidence grade (draft mapping)Grade pendingPart 16, Q228 · Sources: R10
Sources cited
- R10 GRAIL. Full NHS-Galleri trial results presented at the 2026 ASCO Annual Meeting. May 2026; see trial factsheet and presentation. Link pending verification
From Longevity Unmasked by Afshine Ash Emrani, MD, FACC. Medical disclaimer. This book is for education. It is not medical advice, and reading it does not make you my patient or create a doctor-patient relationship. Nothing here is meant to diagnose, treat, cure, or prevent any disease. Medicine is personal: a test, drug, supplement, or exercise plan that helps one person can harm another. Do not start, stop, or change any medication or treatment because of something you read in these pages. Talk with a licensed clinician who knows your history first. If you think you are having a medical emergency, call 911. The author disclaims responsibility for any loss or harm arising from use of the information in this book.