Galleri Multi-Cancer Signal Test

The Galleri test is a next-generation blood test designed to detect signs of multiple cancers early, often before symptoms appear, by analyzing tiny fragments of tumor DNA circulating in the blood. These fragments, called cell-free DNA (cfDNA), are released when cancer cells die and break apart. What makes Galleri unique is its ability to read the methylation patterns on this DNA, chemical tags that help regulate which genes are turned on or off, and use these patterns to identify a cancer “signal” and determine where in the body the cancer likely originated.

The test surveys roughly 100,000 genome regions and over a million CpG sites (locations on DNA where methylation commonly occurs), looking for abnormal patterns linked to cancer. A machine learning algorithm then compares the results to a reference database of cancer and non-cancer profiles to determine whether a cancer signal is present. If detected, it predicts the cancer signal origin (CSO), which is the tissue or organ most likely to be affected.

Galleri does not aim to replace traditional screening methods like mammograms or colonoscopies. Instead, it offers an additional layer of surveillance, especially for hard-to-detect cancers such as pancreatic, ovarian, or esophageal cancers, which are types that often go unnoticed until they are advanced. This is crucial, since the earlier cancer is found, the higher the chances of successful treatment.

In research and early clinical experience, Galleri has shown strong performance, particularly in later-stage or faster-growing cancers. For example, it detected about 73% of plasma cell cancers and 53% of lymphoid cancers in clinical validation studies. Even more importantly, when the test returned a cancer signal, it correctly identified the tissue of origin in over 99% of lymphoid and 100% of plasma cell cancer cases. While detection rates are lower for early-stage cancers (as with many blood-based tests), real-world data show Galleri can still identify stage I cancers in a subset of patients.

In the U.S., Galleri is already being used in select health systems and employer-sponsored programs. Early findings suggest a “cancer signal detected” result appears in about 1% of asymptomatic individuals tested. In those cases, follow-up imaging and biopsies have confirmed cancer in a significant number, often allowing for earlier diagnosis than would otherwise occur.