The FDA approves Grail's Galleri test, a single blood draw that screens for over 50 cancer types with a false positive rate below 1%.
The FDA has granted approval to Grail's Galleri multi-cancer early detection (MCED) test, the first blood-based screening tool capable of detecting over 50 types of cancer from a single blood draw. The approval, supported by data from the landmark PATHFINDER-2 study published in JAMA Oncology, represents a paradigm shift in cancer screening.
The test works by analyzing cell-free DNA (cfDNA) circulating in the bloodstream. When cancer cells die, they release fragments of their DNA into the blood. The Galleri test uses next-generation sequencing and machine learning algorithms to detect cancer-specific methylation patterns in this cfDNA, identifying both the presence of cancer and its tissue of origin.
The PATHFINDER-2 study enrolled 35,000 adults aged 50 and older with no symptoms of cancer. The test detected cancers that had not been identified through existing screening programs in 1.3% of participants. Remarkably, 71% of the cancers detected were types for which no standard screening test exists, including pancreatic, ovarian, liver, and small intestine cancers.
The test demonstrated a positive predictive value of 43%, meaning that nearly half of all positive results were confirmed as true cancers upon diagnostic workup. The false positive rate was 0.5%, meaning fewer than 1 in 200 cancer-free individuals received an incorrect positive result. This low false positive rate was a key factor in the FDA's approval decision.
For cancers detected by the Galleri test, 65% were diagnosed at Stage I or II, compared to only 33% for cancers detected through standard care. Early-stage diagnosis is critical because five-year survival rates for most cancers exceed 80% when caught early but drop precipitously for late-stage disease.
The test is recommended as a complement to, not a replacement for, existing cancer screening guidelines. Patients should continue to receive mammograms, colonoscopies, and other recommended screenings. The Galleri test adds a layer of protection by screening for dozens of additional cancer types simultaneously.
Pricing is set at $949 per test, with an annual screening interval recommended for adults over 50. Several major health insurers have announced coverage plans, and Medicare is conducting an evidence review that could lead to universal coverage for eligible beneficiaries.