A blood test designed to detect signs of multiple cancers in healthy people is now facing its first major regulatory hurdle in the United States. Developed by Grail Inc., the Galleri test looks for tiny fragments of DNA in the blood that are released by tumor cells. This method is part of a new wave of cancer screening that aims to identify various types of cancer using a simple blood sample. The test is currently under review by a group of experts from the U.S. Food and Drug Administration (FDA), who will vote on whether the test's potential benefits for people aged 50 and older outweigh risks like missing cancers or causing unnecessary anxiety from false alarms. Although the FDA did not raise serious safety concerns in documents shared before the meeting, it asked the panel to consider whether the test detects enough early-stage cancers to justify its use for early detection. While the FDA will take the panel’s advice into account, it is not required to follow it. Currently, individuals can pay out-of-pocket for the test, which typically costs $700 or more. However, FDA approval would allow the test to be covered by Medicare and private insurance, greatly increasing its availability. Doctors have mixed views on whether the test is ready for broad use. Dr. Badrinath Konety from the Allina Health Cancer Institute in Minneapolis acknowledges the potential of the technology but advises caution. “The benefit is it may give you a signal,” he said, “but the flip side is you’ve got to chase that signal,” which may involve costly and sometimes inconclusive follow-up tests. The FDA sees the current version of the test as different from the one used in the two major studies that were used to seek approval. To address this, Grail preserved blood samples from those studies and tested them with its newer Galleri test. The FDA submission also includes only the first year of data from a large 140,000-person study in the United Kingdom, which did not achieve its main goal of showing a significant reduction in late-stage cancers. In the data released by the FDA, the Grail test correctly identified cancer in over 66% of people who received a “cancer signal detected.” Over the course of one year, the test found about 30% of cancers that were later diagnosed by doctors. However, the study was not designed to show whether using the Galleri test reduces cancer deaths, which would require years of follow-up. In a separate U.S. study, the Grail test detected a cancer signal in 287 people, and cancer was later diagnosed in 173 of them. The test was more effective at identifying less common cancers like liver and ovarian cancer than more common types like prostate cancer. This raises questions about how impactful the test would be if used widely across the U.S. population. One concern is that people who receive a negative result from the DNA test may skip other recommended screenings, such as mammograms or colonoscopies. While Johns Hopkins scientist Nickolas Papadopoulos calls the test “pretty promising,” he says it will be crucial for doctors to understand its pros and cons and to ensure patients do as well. Many questions remain, such as how often the test should be performed to detect cancer early. “We’re still learning,” he said.