New blood test claims to detect 50-plus cancers before symptoms – but there’s no evidence it can reduce your risk of dying from cancer
A physician who devises screening guidelines for the American Cancer Society explains the pros and cons of the Galleri multicancer early detection test.
The Galleri blood test, developed by biotech company GRAIL, claims to detect over 50 types of cancer before symptoms arise through a single blood draw. While promising, clinical trial data shows the test struggles with early-stage cancer detection and has not been proven to reduce cancer-related mortality or prevent advanced cancer.
In a recent FDA advisory panel vote on September 23, 2026, panelists recommended removing the term "early" from the product labeling due to uncertainty about the test's ability to find cancer at its earliest, most curable stages. The test works by identifying unique DNA methylation markers associated with cancer cells and using machine learning algorithms to generate positive or negative results.
It offers a low false positive rate (0.5%) and high positive predictive value (52% over three annual screens), potentially giving patients more confidence in positive results. However, the test's ability to accurately predict the cancer type is limited, correctly identifying the cancer type in 91% of the 173 patients diagnosed out of 32,000 screened adults.
Despite its strengths, the Galleri test's limitations highlight the need for careful consideration and further scrutiny of the evidence before widespread adoption as a screening tool.
Written by urgent.news from The Conversation's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
