A single blood test that can screen for more than 50 cancers seems to work quite well in the real world, a preliminary study reveals.
The researchers found that of more than 6,600 apparently healthy people aged 50 and over, the blood test detected a possible “signal” of cancer in about 1%. When these people underwent further testing, cancer was confirmed in 38%.
Experts called the results an “important first step” to see how the so-called early detection test for multiple cancers could fit into real-world care.
“It’s not ready for prime time,” said study co-author Catherine Marinac, a researcher at the Dana-Farber Cancer Institute in Boston.
But if more studies confirm the usefulness of the blood test, she said, that could be a game-changer.
The results come from a study called Pathfinder, which is being conducted at several medical institutions across the United States to evaluate the Galleri blood test. It is one of many blood tests developed by various companies, all with the aim of providing a ‘one-size-fits-all’ screening for multiple cancers.
Galleri’s test can screen for more than 50 types of tumours, many of which currently have no routine screening tests, such as pancreatic, liver and ovarian cancers.
But while it may seem like a panacea, there are pitfalls to any cancer screening. One is the risk of a false positive result that leads to further, possibly invasive, testing to find that no cancer is present – and all the anxiety and expense that might come with it.
It’s important, Marinac said, to study not just the performance of tests for early detection of multiple cancers, but also what happens when they’re part of real care.
And ultimately, she said, a drug test must save lives. Much more research will be needed to show whether the cancers detected by these blood tests are less likely to be fatal.
The Galleri test is performed by GRAIL, a California biotechnology company that funds the Pathfinder study. Galleri and similar tests under development work on a basic premise: they look for biological “signals” indicating the possible presence of cancer, such as DNA fragments released by cancer cells into the bloodstream.
Blood tests can also predict where the potential threat is in the body, so doctors can decide which follow-up tests – such as imaging, endoscopies or biopsies – should be used.
The current results are based on more than 6,600 adults aged 50 and over with no known cancer. Just over 1% tested positive on the Galleri test and 38% of them were eventually diagnosed with cancer.
Of all the patients with a positive blood test, more than 90% had more than one imaging test, while half had more than one invasive test – although many of these were carried out in people who have been found to have cancer.
“The diagnostic odyssey,” Marinac said, was longer for people who were ultimately not diagnosed with cancer: in these cases, doctors were usually hesitant to stop the diagnosis after initial tests showed no cancer.
So for these patients, diagnostic “resolution” took a median of 79 days, meaning half waited longer.
Importantly, the researchers found that when the blood test indicated no cancer was present, it was correct 99% of the time.
The results were presented on Sunday at a meeting of the European Society for Medical Oncology in Paris. Studies published at meetings are generally considered preliminary until they are published in a peer-reviewed journal.
“This is very exciting technology,” said Dr. Ruth Oratz, medical oncologist at NYU Langone Perlmutter Cancer Center in New York.
Oratz, who was not involved in the research, said it would be “fantastic” to find many cancers with a single blood test. “But,” she pointed out, “we’re not there yet.”
Cancer screening is complex, Oratz noted. Depending on their risk factors, some people need to start screening earlier, or have more frequent or different tests, for example.
It’s not yet clear, Marinac said, who should be screened with any early detection test for multiple cancers, how often they should be done, or whether the frequency should vary depending on people’s risk factors.
Both experts stressed that people should continue with existing screening tests for diseases like breast, cervical and colon cancers.
Talk to your doctor, Oratz said, about the screenings you should have.
At this time, there are no tests for the early detection of multiple cancers approved by the United States Food and Drug Administration. Galleri is available to doctors on order, as a “laboratory-developed test” – which the FDA has historically not regulated, according to the US National Cancer Institute.
But patients would likely have to pay for the test, the institute says, and possibly any diagnostic tests used to follow up on a positive result.