A simple blood test could one day detect cancer. But there is a problem – National

One day, people might be able to get a cancer test as easily as their cholesterol.

"Liquid biopsy" – a blood test – is an active area of ​​research for the diagnosis of cancer. Although the research is still in its infancy and the test has lasted for years, if not more than a decade, before being available to the general public, experts say it could be useful.

"I think that early detection of potentially early-stage and potentially treatable cancers will potentially change the game," said Dr. John Lewis, Department of Oncology, University of Alberta. .

How does a liquid biopsy test work?

The test detects changes in the bloodstream, such as mutated DNA fragments or specific molecular changes indicating the presence of cancer. At present, cancers are diagnosed through biopsies of tissue samples, a much more invasive method.

Liquid biopsies can be used for a variety of purposes, such as controlling whether an anti-cancer treatment actually shrinks the tumor, customizing treatments based on the patient's particular gene mutation, as well as for detection. At least, that's what the researchers hope.

For a recent study published in Nature, a Toronto-based research team was able to form a computer program to recognize certain chemical changes in the blood of people with cancer at an early stage, and even d & # 39; Identify the type of cancer that the patient had contracted. list of some different types.

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"This opens the door, it is still in the research stage, but it also opens the door to liquid biopsy for early detection of cancer," said co-author of the study, Daniel De Carvalho , senior scientist at the Princess Margaret Cancer Center.

Another study, published in Science early 2018, also showed promising results for a cancer detection blood test, which identified eight different cancers with a median success rate of 70% in over 1,000 patients.

These procedures have yet to be improved, refined and tested before being published in the mass market, said De Carvalho, and it will take years. But he thinks that early identification of cancer could make a big difference for some people.

"The sooner we identify cancer, the easier it is to treat the patient."

For these tests, "the goal is to detect it as long as the tumor is so small that you can remove it," said Rayjean Hung, a Canada Research Chair in Integrative Molecular Epidemiology in the Health System. from Sinai to Toronto.

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Another co-author of the Nature study, Hung, believes that liquid biopsies could be particularly useful for patients with lung cancer, pancreatic cancer or other rapidly growing aggressive cancers, for whom early detection has a significant Results of treatment.

Treat cancer

Treatment remains a big question though. What do you do if you find cancer but can not do anything about it?

"It's a very active discussion right now," Lewis said.

"If we know that something exists and we do not have a clear clinical path, is this information useful?"

In prostate cancer, for example, PSA (prostate-specific antigen) tests have been criticized for leading to overdiagnosis.

"The PSA test, for example, has allowed many men to test their prostate cancer earlier, but the PSA screening has the side-effect of diagnosing many men with one-up symptoms. non-aggressive, indolent prostate cancer, "he said. I said. This test has been criticized for leading to unnecessary additional tests or even treatments for something that may never have caused a problem.

"With the diagnosis of cancer, there is diagnosis-based anxiety and burden, and in general, most people want to do something about it. Often, there is no clear clinical benefit or even option to treat. "

This is less of a problem in aggressive forms of cancer, such as lung cancer, Hung said. "We rarely see lung or pancreatic cancer instead. So, for those, overdiagnosis becomes less of a problem. But that's a problem for other types.

It is also unlikely that these tests will lead directly to a cancer diagnosis, she said. Instead, patients should probably undergo a CT scan and other imaging tests after a positive result.

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De Carvalho hopes that, thanks to his computer program allowing him to better recognize different cancers, he will be able to know those who will not cause serious medical problems and who will identify them, and to identify them accordingly.

For less aggressive cancers such as prostate cancer, the important thing is to identify the cancers that will kill the patient, not whether the patient has cancer, said Lewis.

"So, the liquid biopsy and the whole field will have to be more specific than" Do I have cancer? ". They should also be specific: "Do I have an aggressive cancer that I have to act on? & # 39; "