Test makers have hailed a simple blood test that detects more than 50 types of cancer as a new approach to cancer screening, but Canadian medical experts have warned that the technology needs more work.
Earlier this month, Grail – a US biotech company – announced the latest results from their study on the Galleri blood test, a test for the early detection of multiple cancers (MCED).
The test is designed to find multiple types of cancer through a blood sample by looking for cancer signals on DNA that cells drop into the bloodstream.
In the company Recent clinical trial of its productthey found that out of about 6,600 people over the age of 50, testing revealed possible cancer in 92 people.
Of those 92 people, most – 62 percent – did not have cancer after they were followed up with further tests including imaging, scans and biopsies. Some of the people reported had cancer, with 35 people diagnosed with cancer.
“The fact that we’ve already detected these cancers – 71 percent of them don’t have screening options available – I thought was fantastic,” said Dr. Jeffrey Michael Finstrom, Grail’s chief medical officer.
Of the 6,500 study participants who were not identified by a blood test, 86 developed cancer in the next 12 months, found through conventional screening methods. It’s not clear how many cancers may actually have been in that group but not detected on testing and screening.
The results have not been published in a peer-reviewed journal.
More trials to come
The Galleri test is one of the first MCED tests available in the United States with a doctor’s prescription. Although not yet available in Canada, MCED tests like the Galleri are getting attention because they may be useful if they are shown to help prevent cancer deaths, The American Cancer Society says.
Recently, US President Joe Biden announced further review of these tests with a government-funded clinical trial Effectiveness of multiple types of early screening tests.
The Galleri test has also caught the attention of the NHS in England, and it is Partnership with Grail In a three-year trial to test Gallery Test and its effectiveness on 140,000 volunteers. Early results are expected next year.
It may be years before we see such tests in Canada. For those studying early cancer detection and overdiagnosis, they say it’s too soon to know if and how common a test like this one could be in Canada.
One researcher says his worry about Gallery’s test is that it doesn’t find all cancers.
“For large tumors, the test is very effective and you can detect it. But if the tumor gets smaller and smaller, the test will not be very effective,” said Dr. Eleftherios Diamandis, a professor in the University of Toronto’s Department of Laboratory Medicine. Medical biochemist at Mount Sinai Hospital and University Health Network in Toronto.
Diamandes says, based on his research, that false positives on the test are also a problem.
“If you are interested in taking this test, you must understand that no test is perfect [that] I can tell you: you have cancer or you don’t have cancer,” he said.
“Tests are imperfect…and it’s too early to say if Galerie’s test is good enough to solve this century-old quest to find biomarkers that address the presence of early-stage cancer.”
That’s why Diamandis and other Canadian experts say the test needs more scrutiny and independence before it can be used clinically, which could take years from now.
“We need of course to be enthusiastic about these tests, but they need to be evaluated in a rigorous way where we know exactly what the benefits or harms are, so that when people think about having these tests, they know what they are doing,” said Dr. Eddie Lang, chief of emergency medicine for the Calgary region at Alberta Health Services. And the professor at the University of Calgary: “They deal with.”
Blood tests to detect cancer
Early detection of cancer is a key factor in reducing the number of cancer-related deaths. In Canada, although the overall rate of new cancer cases is declining, the number of cancer diagnoses and deaths continues to grow due to population aging and population growth.
About 233,900 people in Canada will be diagnosed with cancer, and 85,100 cancer-related deaths are expected this year alone. According to Statistics Canada.
Watch | A blood test detects cancer in healthy people, the company says:
The Gallery test is just one of several tests being tried in the hope of detecting cancers in their early stages.
Venstrom says there are plenty of benefits to testing, including early detection.
In Grylls’ recent Pathfinder study, about half of the 36 cancers detected in 35 people were at an early stage.
“This means that these patients are more likely to continue potentially curative treatment and achieve significantly better outcomes,” Finnstrom said.
The Galleri test is only available in the United States
A spokesperson for Health Canada told CBC News that the federal health authority does not regulate testing services nor tests developed by public or private laboratories for use at home.
Provinces and territories are responsible for testing services.
Be a very careful consumer
Diamandes says he and his colleagues have been studying the Grail and Galleri test for about seven years.
Based on the results they reviewed, Diamandes says the test isn’t ready for clinical use as there are still some unknowns, like the number of missed cancers and the false-positive rate.
Finnstrom says the test’s false-positive rate is less than one percent.
Both Diamandes and Lange say that overdiagnosis is a concern for any early detection tests.
“You find something…it’s there, but it wouldn’t do you any harm if you didn’t know about it before,” Lang said.
This is well known, he says, with prostate cancer screening and mammography screening for breast cancer.
“There is always a risk that you will find a small, slow tumor that will never grow, never spread, and never catch your eye unless you look for it in the first place. So I think the main thing is for people to be aware of the risks.”
That’s why he and Diamandes say blood tests to detect multiple cancers need rigorous study by independent bodies that can provide guidance on any potential use.
“Unless there’s a recommendation that you should go ahead and get these things, I’d be a very careful consumer of these tests because once you take the test and know the result, you might be going down a path that you’ll regret,” Lang said.