One day, people may be able to take a cancer test as easily as having their cholesterol checked.
"Liquid biopsy" – a blood test – is an active area of research for the diagnosis of cancer. While the research is still in the early stages and the test is for years, perhaps more than a decade, far from being available to the general public, experts say it can be valuable.
"I think for the early detection of cancers that are deadly and potentially curable in the early stage, this will potentially change the game," said Dr. John Lewis of the oncology department at the University of Alberta.
How a Liquid Biopsy Test Works
The test works by detecting changes in the bloodstream, such as fragments of mutated DNA or specific molecular changes that indicate the presence of cancer. Now, cancers are diagnosed through biopsies of tissue samples, a much more invasive method.
Liquid biopsies can be used for a number of purposes, such as monitoring whether a cancer treatment is actually shrinking the tumor, to tailor treatments based on a patient's specific genetic mutation as well as for detection. At least that's what the researchers expect.
For a recent study published in Nature, a Toronto research team was able to train a computer program to recognize some chemical changes in the bloodstream for people with early-stage cancer and even identify what type of cancer the patient had. list of some different types.
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"This opens the door, it's still in the research phase, but it opens the door to liquid biopsy for early detection of cancer," said study co-author Daniel De Carvalho, a senior scientist at the Princess Margaret Cancer Center.
Another study, published in Science in early 2018, also showed promising results for a blood test that detects cancer, which was able to identify eight different cancers, with an average success rate of 70% in over 1,000 patients.
These procedures still need to be perfected, refined, and tested before they reach the mass market, De Carvalho said, and that will take years. But he thinks that identifying cancer early can make a big difference for some people.
"The earlier we identify the cancer, the easier it will be to treat the patient."
For these tests, "The goal is to find it while the tumor is so small that you can take it off," said Rayjean Hung, president of Canada's research on integrative molecular epidemiology at the Sinai Health System in Toronto.
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Hung, who is another co-author of the Nature study, believes that liquid biopsies may be particularly useful for patients with rapidly growing lung, pancreas or other aggressive cancers, where early detection makes a big difference in treatment outcomes.
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"It's a very active discussion now," Lewis said.
"If we know that something is there and we do not have a clear and clear clinical path, is this information helpful?"
In prostate cancer, for example, PSA (prostate specific antigen) tests have been criticized for leading to overdiagnosis.
"The PSA test, for example, allowed many men to test their prostate cancer earlier, but the side effect of PSA screening has been that many men with non-aggressive, indolent prostate cancer have also been diagnosed," he said. This test was criticized for leading to additional unnecessary testing or even treatments for something that may have never caused a problem.
"With the diagnosis of cancer, there is anxiety and overload based on the diagnosis and usually most people want to do something about it. Often there is no clear clinical benefit or even an option to treat. "
This is a minor problem in aggressive forms of cancer, such as lung cancer, Hung said. "We rarely see any cancer in the lung or pancreas that is there. Therefore, for those, overdiagnosis becomes a minor problem. But it's a problem for the other guys. "
Such tests would also be unlikely to lead directly to a diagnosis of cancer, she said. Instead, patients would probably have to do CT scans and other imaging tests after a positive result.
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De Carvalho hopes that as his computer program is trained to better recognize different cancers, he will know which ones will not lead to serious medical problems and which will be, and will identify them accordingly.
For less aggressive cancers, such as prostate cancer, the important thing is to identify which types of cancer will kill the patient, rather than whether the patient has cancer, Lewis said.
"So, the net biopsy and the whole field will have to be more specific than," I have cancer? Will it have to be specific about: & # 39; Do I have an aggressive form of cancer that I need to take action? & # 39; "
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