The day is not far off when a simple blood test will mean that people with cancer will no longer have to undergo surgery to remove cancerous tissue—commonly known as a biopsy—in order to monitor their disease or even diagnose it.
The blood test then becomes what experts in the field call a liquid biopsy. “We collect DNA from the cancerous tumour in the blood, so it’s a standard blood test. But in a blood sample, there may be 40 billion red blood cells, yet only five cells from the tumour circulating in the blood,” explains Stéphanie Lord-Fontaine, vice president of scientific affairs at Génome Québec.
“It’s like finding a needle in a haystack, and we have to optimize that process. After that, we have to sequence those five cells to determine the tumour’s genetic profile,” explains Lord-Fontaine, whose organization recently announced a $200,000 grant for a research project totaling just over $650,000, aimed at refining this liquid biopsy technology to the utmost—a technology that already exists but is not yet precise enough.
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This research is being conducted in collaboration with the CHUM, but it is an engineer who is leading the effort. That person is Alexandre Pellan-Cheng, a biomedical engineer at the École de technologie supérieure. “Many problems in the medical field require a certain level of engineering expertise. We’re involved in the development of diagnostic tests, and what we’re really trying to do is amplify a disease signal,” he explains.
“Cancer cells have DNA, just like all the cells in the human body, and these cells die. When they die, the proteins and all the cellular material, including the DNA, are released into the bloodstream, which is why a blood draw could capture this circulating cancer DNA for detection. It may sound a bit futuristic, but clinical tests exist and can be ordered in hospitals specifically to monitor and detect cancer in patients. It’s something that’s already very common.”
“The problem,” he continues, “is that while it does work, it’s not yet perfected. We get a lot of false negatives—that is, tests that come back negative, but the patients still have cancer. There’s a real opportunity to advance research and innovate to improve these tests and enhance patient care.”
For now, the research focuses on four types of cancer—lung, head and neck, and ovarian—in which the CHUM has developed significant expertise. “What’s unique about this project is that they want to eliminate the sequencing of the tumour removed by the surgeon—that is, eliminate the initial step where we first have to sequence the tumour collected during surgery and replace that step with a blood draw,” says Lord-Fontaine.
Could surgical biopsies eventually be eliminated entirely? “That would be a scientist’s dream,” says Pellan-Cheng, “but the idea isn’t necessarily to replace them. There are certain cancers—like lung cancer—where a biopsy is actually almost impossible because the cancer is in a location that’s hard to reach with a needle, and the sample might even be of very poor quality. In fact, this biopsy can help the pathologist assess the disease, but it may not be sequencable, and that’s where we’re adding a tool to clinicians’ toolbox to provide the same quality of care to patients, even if the cancer isn’t biopsable.”
Why is this sequencing so important? Because no two cancers are alike, emphasizes Lord-Fontaine. “For each tumour and each patient, the mutations differ. Whenever a mutation is present, we can assign a targeted treatment, but this varies from one individual to another. This is what we call precision oncology. So it really involves tailoring treatments based on the patient’s tumour DNA.”
This is what the diagnostic tests that Pellan-Chang is developing will make possible, she explains. “We’ll examine the entire DNA—that is, the complete sequencing of the tumour’s genome—and identify which mutations are present in the circulating tumour cells. We can then better select the targeted therapy needed to spare healthy cells and deliver a treatment that is much more precisely tailored to the mutations present.”
“This is really exciting for an oncologist,” says Lord-Fontaine. “There’s no need for surgery along the way to monitor treatment; we can better select the therapy based on the mutation found in the sample; and we can also track the response to treatment and the risk of relapse later on, once the patient is in remission. We can take a blood sample and see if any tumour markers appear. This is a significant development, but we really need to optimize the technology.”
Since certain treatments—such as immunotherapy—can be tailored using genomics, “if we can see the tumour DNA, we can select a treatment that is much less aggressive and spare a patient from chemotherapy or radiation therapy and all the side effects that come with them.”
It is still too early to say when it will be possible to detect all cancers with a blood test, both for diagnosis and monitoring, but Pellan-Cheng notes that there are “certain types of liquid biopsies already available in Quebec—approved and covered by insurance, particularly for lung cancer— so we already have something that exists and can be used, but we are looking to improve these tests.”
The fact that these tests already exist has made it easier to secure funding to further this research, the engineer points out. “Since the concept works and has already been proven, it saves me from having to justify the need for a test, but it also shows that there are sometimes gaps in the tests and room for improvement.”
Lord-Fontaine summarizes the objective of the ongoing work as follows: “We need to optimize the technology in terms of sensitivity because it still requires a high tumour burden in the blood to be able to detect it. So at the very beginning of cancer, before symptoms appear, the technology isn’t yet sensitive enough to detect cancer at the time of diagnosis early in the disease process.”
–This report by La Presse Canadienne was translated by CityNews
