The Galleri test, developed by Grail Inc., does not diagnose cancer. Instead, it analyzes a blood sample for signals that may indicate the presence of one of several types of tumors. People who receive a positive result would require further medical tests to determine whether they actually have cancer.
An advisory panel to the US Food and Drug Administration voted 7-2, with one member abstaining, in favor of the test's potential benefits outweighing its possible risks. These risks include false reassurance and unnecessary fear or anxiety.
The panel also raised several questions about the technology that require further research.
Dr. Victor Van Berkel, affiliated with UofL Physicians in Louisville, Kentucky, said his support may be based partly on hope and stressed that additional research would still be necessary even if the test is approved for general use.
The decision followed two earlier votes in which experts said the test appeared to be safe and effective for people aged 50 and above.
Several companies around the world are developing similar blood tests. Wednesday's vote is significant because it marks the first time a federal advisory body has backed the experimental approach. The FDA is not required to follow the panel's recommendation, but approval could pave the way for wider use of the technology in the United States. A final decision is expected in the coming months.
Current cancer screening methods, including mammograms and colonoscopies, generally focus on detecting specific types of cancer. The panel, however, objected to Grail's use of the term “early detection,” saying the company had not adequately demonstrated the claim.
Experts said the test should not replace existing routine cancer screenings and should instead be used as an additional tool. They also stressed that a negative result does not guarantee that a person does not have cancer.
Further research is also needed to determine whether the test provides benefits comparable to established screening methods such as mammograms.
The Galleri test is already available for purchase in the United States, typically costing $700 or more, which patients generally pay themselves. If the FDA grants formal approval, access could expand because Medicare and private insurers may then cover the cost.
FDA experts and outside advisers spent hours discussing potential risks, including the possibility that the test could miss many genuine cancer cases or incorrectly suggest cancer in healthy people.
The test has also shown lower accuracy in detecting early-stage cancers, even though treatment is generally more effective when cancer is identified at an early stage. Grail has not yet provided evidence showing that screening with the test reduces cancer deaths, as establishing such an outcome would require following patients for many years.
Grail representatives said the test represents a major advance because it can detect signals associated with more than 50 types of cancer, including dozens for which there are currently no effective screening methods, such as liver and ovarian cancer.
Grail's main study involved 140,000 older adults. According to the study, the test detected about one-third of cancers diagnosed during the following year. Among people whose results indicated a “cancer signal detected,” about two-thirds were later found to actually have cancer.
However, FDA reviewers presented the same data from a different perspective, highlighting potential harms. The agency's lead reviewer noted that the test failed to detect two out of every three cancers diagnosed during the following year, raising concerns that many people could receive false reassurance.
Consumer advocacy groups have also warned that people who receive a normal result from a DNA-based test could ignore early symptoms of cancer or delay seeking medical care.
Diana Zuckerman of the nonprofit National Center for Health Research said during public comments that people might delay visiting a doctor when symptoms begin, and even a short delay could have serious consequences. She questioned whether people would continue undergoing other recommended cancer screenings after receiving a negative result.
