A single blood test screening for more than 50 cancers substantially increases cancer detection when added to standard screenings, according to a study published in Nature Medicine by researchers at the Oregon Health & Science University Knight Cancer Institute. GRAIL’s Galleri test was assessed in the PATHFINDER 2 study, utilizing a machine-learning algorithm to analyze chemical patterns that differentiate cell-free DNA from cancerous cells compared to those from healthy cells.
PATHFINDER 2 Study Results and Cancer Detection Rates
Based on OHSU data, the PATHFINDER 2 trial was the largest interventional multi-cancer early detection study conducted in North America, recruiting 35,878 adults aged 50 and older from Canada and the United States. OHSU served as the leading enrollment site, signing up approximately 6,100 participants through its Knight Early Detection Clinical Research team. Results showed that adding Galleri to standard clinical screening for breast, colorectal, cervical, and lung cancers increased the number of screen-detected cancers by 6.5-fold, based on findings presented by lead author Dr. Nima Nabavizadeh.
Did you know? Seven out of ten cancers newly detected by the Galleri test in the PATHFINDER 2 trial had no national screening recommendations, targeting deadly malignancies like pancreatic, ovarian, and liver cancers that typically only present symptoms at advanced stages.
Accuracy and False-Positive Rates of the Galleri Test
The Galleri test demonstrated a specificity of 99.64%, resulting in a false-positive rate of just 0.36%, according to OHSU researchers. Out of 287 participants who received a positive cancer signal, 173 were ultimately diagnosed with cancer, yielding a positive predictive value of 60.3%. Furthermore, the machine-learning algorithm correctly predicted the location of the cancer in the body 91.3% of the time, helping clinicians guide diagnostic testing efficiently. Safety evaluations among more than 35,000 participants showed that only 0.6% underwent an invasive procedure following a positive result, with the majority of those procedures remaining nonsurgical.
Comparative Insights From the United Kingdom NHS-Galleri Trial
Real-World Patient Impact and Early Intervention
Real-world outcomes illustrate the clinical utility of finding malignancies before symptoms appear. Franklin Weingarten, a retired Oregon physician and study participant who enrolled at OHSU when he was 84, received a positive Galleri signal that pointed to his liver. Doctors subsequently diagnosed him with cholangiocarcinoma, a rare bile duct cancer without routine screening options. Because the cancer was localized, surgeons removed part of his liver, leaving Weingarten cancer-free at age 88.
Future Multi-Cancer Early Detection Studies
Frequently Asked Questions
What does the Galleri blood test screen for?
The Galleri test screens for more than 50 types of cancer by analyzing circulating cell-free DNA and examining chemical patterns using a machine-learning algorithm, according to OHSU research.
Does the blood test replace standard cancer screenings?
No. According to study authors, the test is designed as a complement to, rather than a replacement for, standard routine screenings for breast, colorectal, cervical, and lung cancers.
What was the false-positive rate in PATHFINDER 2?
The study reported a specificity of 99.64%, equating to a false-positive rate of just 0.36%, with a positive predictive value of 60.3% among participants who received a cancer signal.
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