Federal health advisers on Wednesday endorsed a blood test that seeks to detect signs of various types of cancer in apparently healthy people, although they cautioned that it is not yet entirely clear how well the technology will work.
The Galleri test from Grail Inc. does not diagnose cancer, but rather, with a single blood draw, it looks for signs that a person may have one of the tumors included in an extensive list. Those who test positive would need additional care to determine if they are truly sick..
The advisory panel of the Food and Drug Administration (FDA) considered in a 7 to 2 vote that the DNA-based test offers more potential benefits than risks, such as generating false assurances or raising unsubstantiated alarms. The yes vote came despite the panel raising many questions about the technology that require further study.
“Perhaps my ‘yes’ is more of a show of hope than a precise decision,” said Dr. Victor van Berkel, of UofL Physicians in Louisville, Kentucky, describing how more research is needed even if the test is put into practice. “If we can detect more early-stage cancers in the population that we currently can’t detect through screening, that will end up being beneficial.”
The vote followed two previous votes in which experts said the test appears safe and effective for use in people 50 and older.
Many companies are investigating this type of blood test, and Wednesday’s vote marks the first time a federal advisory group has endorsed this experimental approach. The FDA is not required to follow the advice, but if it accepts it, it could pave the way for widespread adoption in the United States of a long-sought method to detect more cases of cancer early. A final decision is expected in a few months.
Today there are a few recommended cancer screening tests, such as mammograms and colonoscopies, that look for one type of tumor at a time.
Those tests are designed to detect tumors in their early stages, when they are easier to treat, and the panel was reluctant to use that term for the Grail test, arguing that it had not been proven effective for “early detection.”
Experts also developed a list of precautions that should be communicated to doctors and potential patients, including: The test should be used as a complement to current routine cancer screenings, not as a replacement. A negative result does not guarantee that you do not have cancer. And more studies will be needed to show whether the test is as beneficial as more common cancer screenings, such as mammograms.
In the United States, you can now purchase the Galleri test—generally paying $700 or more in cash. However, FDA approval would likely expand its availability by opening the door to coverage by Medicare and private insurers.
FDA staff and other outside experts spent hours debating the potential downsides of the technology.
Among the risks is the possibility that the test will miss a significant number of real cancers while flagging a possible one in patients who are healthy. The test was also less accurate at detecting the early stage, when treatment is simpler and more likely to benefit patients. Grail also did not provide data showing that testing its test reduced the number of cancer deaths, an indicator that would have required years of follow-up.
Grail representatives argued that their test represents a breakthrough because it can detect signs of more than 50 types of cancer, including dozens for which there are no screening options, such as liver and ovarian cancer.
“Patients want opportunity, they want options,” said Dr. Mylynda Massart of the University of Pittsburgh, who presented on behalf of Grail. “They want the opportunity to fight their disease while there is still a chance of survival.”
Grail’s main study, conducted in 140,000 older adults, showed that its test detected about a third of cancers diagnosed over a one-year period. About two-thirds of patients who received a “cancer signal detected” result were later confirmed to have the disease.
However, FDA reviewers present at the meeting turned the company’s data on its head to emphasize potential downsides to that performance. The agency’s top analyst noted that the test missed 2 out of every 3 cancers that were diagnosed over the next year, giving many patients a false sense of security.
Consumer advocates warned that patients could ignore early signs of cancer after receiving a negative DNA test result.
“When they start having symptoms, there will be a tendency to delay going to the doctor — just a little bit — and that could be deadly,” added Diana Zuckerman of the nonprofit National Center for Health Research, who spoke during a public comment period. “They will be told to continue with other screenings, but will they?”
