Grail's cancer blood test faces high-stakes FDA review

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WASHINGTON (AP) — A blood test designed to spot signs of multiple cancers in apparently healthy people faces its first major regulatory hurdle Wednesday as advisers to the U.S. government review how well it works.

Grail Inc.'s test looks for DNA fragments shed by tumor cells, an emerging approach to screening that aims to detect various cancers with a single blood draw.

Cancer screening is supposed to spot tumors in their early stages, when they're easier to treat. A multi-cancer screening test would be a departure from the handful of currently recommended cancer tests — including mammograms and colonoscopies — that look for one cancer at a time.

A panel of Food and Drug Administration advisers will vote Wednesday on whether the proposed benefits of Grail's Galleri test, designed for people 50 and older, outweigh risks such as missing cancers or causing false alarms.

In documents posted ahead of the meeting, FDA staffers didn't raise major safety concerns, but they want the panel to discuss whether the test picks up enough early stage cancers to be marketed for “early detection.”

The FDA will weigh the advisers' recommendations but is not required to follow them.

People in the U.S. can already buy the test, typically by paying $700 or more out of pocket, because the government allows limited use of certain laboratory-based tests. But FDA approval promises to widen availability by opening the door to coverage from Medicare and private insurers.

Oncologists are divided on whether the test is ready for widespread use. Dr. Badrinath Konety of Allina Health Cancer Institute in Minneapolis says there's “a lot of promise” in the technology but has cautioned patients who've asked about it.

“The benefit is it may give you a signal," he said. “The flip side now is you’ve got to chase that signal,” which can involve additional pricey tests that may not give a clear answer.

FDA's panel will have to consider those downsides and a number of other unusual aspects of the Sunnyvale, California-based company's technology.

For one thing, the FDA considers the company's current test a completely different product than the one it used in two large studies conducted to win approval. To bridge the gap, the company saved frozen blood samples of people enrolled in those studies and then tested them with its newer Galleri test.

Also, the company's FDA submission only includes the first year of data from its primary study. That 140,000-person study was conducted in the U.K. and failed its main goal of showing a statistically significant reduction in late-stage cancers. That failure is not mentioned in FDA's review, but it's almost certain to come up during Wednesday's discussion.

In the study data released by FDA this week, Grail's test accurately predicted cancer in more than 66% of patients who received a “cancer signal detected." During the one-year period, the test detected about 30% of cancers that would later be diagnosed by physicians.

The study, conducted with the U.K.'s National Health Service, was not intended to show that screening with Galleri reduced cancer deaths. That approach would have required many more years of follow-up.

In a newly published analysis of a separate U.S. study, the Grail test detected a cancer signal in 287 people. Cancer was eventually diagnosed in 173 of them.

The test was better at finding less common cancers, such as liver and ovarian cancers, compared with more common forms of the disease like prostate cancer. That raises questions about the wide-scale impact of deploying the test for millions of Americans.

One worry is that people who get an all-clear from DNA testing test might skip guideline-recommended screenings like mammograms or colonoscopies.

Johns Hopkins scientist Nickolas Papadopoulos considers Grail's test “pretty promising” but said that if the FDA clears it, it will be vital for doctors to understand the pros and cons and to make sure their patients do, too.

Among many questions yet to be answered, he said: “If we do this test once a year, once every three years, is that good enough to eventually catch the cancer early? We’re still learning.”

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