Source: French to English Tester Published on: 2026-04-06
Source: The Conversation – in French– By Alexandre Pellan Cheng, Associate Professor, Department of Systems Engineering, École de technologie supérieure (ÉTS)
A simple blood test to detect cancer even before the appearance of symptoms: this is the promise of liquid biopsy, a rapidly growing technology that could revolutionize the diagnosis, monitoring, and personalization of oncological treatments.
Cancer is now the leading cause of death in Canada. Two out of five Canadians will develop cancer during their lifetime, and one in four will die from it. Every day, nearly 700 people are diagnosed with cancer in the country. According to theCanadian Cancer Society, the most frequently diagnosed cancers are those of the lung, breast, prostate, and colorectal cancer.
These figures conceal an essential reality: survival varies greatly depending on the type of cancer and, above all, the stage at the time of diagnosis. Thestatistical dataclearly show that the chances of survival decrease as cancer is detected at a more advanced stage. These data highlight the urgency of better detecting the disease, and above all, detecting it earlier.
A blood test rather than a scalpel
It is in this context that my research is framed. As a professor of systems engineering at ÉTS Montreal and principal investigator in the cancer axis at the CHUM Research Center, I work on liquid biopsy, an approach that aims to detect cancer from a simple blood sample by analyzing the DNA released into the bloodstream by tumor cells.
Unlike traditional biopsies, which require the removal of a tissue fragment from the tumor, liquid biopsy relies on a simple and minimally invasive procedure: a blood draw is sufficient. Theadvantages of this approachare a reduction in pain, risks for the patient, and the logistical burden associated with hospital procedures. Furthermore, the simplicity of the test would allow for more frequent repeat analyses. Finally, unlike many diagnostic procedures, the blood sample does not require specialized facilities and can be carried out in any care setting, whether it is a local clinic or a CLSC.
In medicine, biomarkers often refer to measurable indicators that can provide information about a person’s health status. The measurement of PSA (prostate-specific antigen), used for decades to monitor prostate cancer, is a well-known example. An elevation of PSA in the blood can indicate the presence of cancer, its progression, or a relapse after treatment.
But this biomarker also illustrates the limits of the approach: PSA is not specific to cancer and can increase for other reasons, which complicates the interpretation of the results.
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Liquid biopsy fits into this same logic, but at a different level of precision. Rather than measuring a protein indirectly linked to the disease, it aims to directly detect the genetic traces left by the tumor cells themselves. In this sense, theTumor DNACirculating can be seen as a much more specific biomarker, carrying information about the nature of the cancer and its progression.
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The smaller a tumor is, the less DNA it releases into the blood. Yet, it is precisely at these very early stages that diagnosis has the greatest impact on survival chances. My goal is to detect these extremely weak signals, sometimes well before the appearance of clinical symptoms, or even after treatment, when the cancer seems to have disappeared but may persist in a residual state.
Tailor treatments to each tumor
Liquid biopsy also allows treatments to be adapted to each patient. By identifying the specific mutations of a tumor, it becomes possible to choosetargeted therapies, better adapted to the genetic profile of the cancer. This approach paves the way for more precise medicine, which takes into account the biological characteristics specific to each disease.
Another major advantage is the ability to track cancer progression over time. If liquid biopsies are repeated before, during, and after treatment, it is possible to observe whether tumor DNA levels decrease or increase. This information can help determine quickly if a therapy is effective or if it needs to be adjusted, thereby avoiding unnecessary treatments and their side effects.
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When the signal gets lost in the noise
While liquid biopsy offers promising prospects, it also poses significant challenges in technological and methodological terms.
One of the main obstacles is the detection of tumor DNA amidst a huge background noise of normal DNA. The mutations sought are sometimes at the limits of the precision of sequencing machines. In my laboratory, we work on reducing technical errors and developing algorithms capable of distinguishing a true cancer mutation from a false signal generated by sequencing technologies, notably through artificial intelligence approaches.
A single blood sample can generate terabytes of data. For each patient, there are billions of DNA fragments to analyze, filter, and compare. The management and analysis of this massive data require robust bioinformatics tools capable of processing information quickly and accurately.
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The quality of the analysis also depends on the preparation of the samples. Circulating DNA is often fragmented and degraded. It must be purified, experimental biases corrected, and made usable by sequencing technologies even before the computational analysis step.
A revolution in progress
For me, liquid biopsy represents much more than a technological tool: it is an opportunity to transform the way we detect and monitor cancer. By combining less invasive methods, earlier detection, and more personalized medicine, it could improve both the quality of life of patients and their chances of survival.
Before becoming a common practice, these approaches will nevertheless have to demonstrate their effectiveness in rigorous clinical studies. But as sequencing technologies advance, what was yesterday science fiction is gradually becoming reality. I am convinced that one day, a simple vial of blood could play a central role in the fight against cancer.
Alexandre Pellan Cheng received funding from the École de technologie supérieure, the CHUM Research Center, the Montreal Cancer Institute, the Mirella and Lino Saputo Foundation, Genome Quebec, and the Mitacs Foundation for liquid biopsy research projects. He is a member of the Montreal Cancer Institute and a researcher at the CHUM Research Center. He is named as an inventor on patents, some of which have been licensed for commercialization by Eurofins-Viracor.
–ref. A simple blood test to track cancer –https://theconversation.com/a-simple-blood-test-to-track-cancer-279644