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By Rodrigo Santos Andrade
A simple blood test could detect cancer
visibility comment0 event October 29, 2026 timer 11:15
A simple blood test to detect cancer before symptoms even appear: that’s the promise of liquid biopsy, a rapidly developing technology that could revolutionize the diagnosis, monitoring and personalization of cancer treatments.**
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Cancer is now the leading cause of death in Canada. Two in five Canadians will develop cancer during their lifetime, and one in four will die from it.
Every day, nearly 700 people across the country are diagnosed with cancer. According to the Canadian Cancer Society, the most commonly diagnosed cancers are lung, breast, prostate and colorectal cancer.
These figures mask a key reality: survival rates vary greatly depending on the type of cancer and, above all, how advanced it is at the time of diagnosis.
The statistical data clearly show that survival rates decrease when the cancer is detected early. These data highlight the urgent need to improve detection of the disease and, above all, to detect it earlier.
A blood test instead of a scalpel
This is the context where my research takes place. As a professor of systems engineering at ÉTS Montréal and principal investigator in the cancer research division at the CHUM Research Centre, I am working on liquid biopsy. This approach aims to detect cancer from a simple blood test by analyzing the DNA that tumour cells release into the bloodstream.
Unlike conventional biopsies, which require removing a tissue sample from the tumour, liquid biopsy relies on a simple, minimally invasive procedure: a blood test is all that’s needed.
The advantages of this approach include reduced pain, lower risks for the patient and less logistical burden associated with hospital procedures. The simplicity of the test also allows for more frequent testing. And finally, unlike many diagnostic procedures, taking a blood sample does not require specialized facilities. Blood can be taken in any health-care setting, whether it’s a local clinic or a community health centre.
In medicine, the term “biomarkers” is often used to refer to measurable indicators that provide information about a person’s state of health. The PSA (prostate-specific antigen) test, which has been used for decades to monitor prostate cancer, is a well-known example. Elevated PSA levels in the blood may indicate the presence of cancer, its progression, or a recurrence after treatment.
However, the biomarker approach does have limits: PSA is not specific to cancer and test levels can rise for other reasons, which can complicate the interpretation of results.
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Detecting the invisible
Liquid biopsy follows the same logic, but at a different level of precision. Rather than measuring a protein indirectly linked to the disease, it directly detects the genetic traces left by the tumour cells themselves.
In this sense, circulating tumour DNA 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 the tumour, the less DNA it releases into the blood. Yet it’s precisely at these very early stages that diagnosis has the greatest impact on survival chances. My aim is to detect these extremely weak signals, sometimes well before the onset of clinical symptoms, or even after treatment, when the cancer appears to have disappeared but may persist in a residual state.
Tailoring treatments to each tumour
Liquid biopsy also makes it possible to tailor treatments to each patient. By identifying the specific mutations in a tumour, it becomes possible to select targeted therapies that are better suited to the cancer’s genetic profile.
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 monitor the progression of cancer over time. By repeating liquid biopsies before, during and after treatment, it’s possible to observe whether tumour DNA levels are decreasing or increasing. This information can help to quickly determine whether a therapy is effective or needs to be adjusted, thereby avoiding unnecessary treatments and their side effects.
When the signal gets lost
While liquid biopsy offers promising prospects, it also poses significant technological and methodological challenges.
One of the main obstacles is detecting tumour DNA amid a vast background of normal DNA. The mutations we are looking for are sometimes at the very limit of the accuracy of sequencing machines. In my laboratory, we are working to reduce technical errors and develop algorithms capable of distinguishing between a genuine cancer mutation and a false signal generated by sequencing technologies, notably through artificial intelligence approaches.
A single blood sample can generate terabytes of data. For each patient, this amounts to billions of DNA fragments to be analyzed, filtered and compared. The management and analysis of this massive data set require robust bioinformatics tools capable of processing the information quickly and accurately.
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The quality of the analysis also depends on sample preparation. Circulating DNA is often fragmented and degraded. It must be purified, experimental biases must be corrected, and it must be made suitable for sequencing technologies even before the computational analysis stage.
A revolution in the making
In my view, 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 patients’ quality of life and their chances of survival.
Before becoming standard practice, however, the effectiveness of these approaches will need to be demonstrated in rigorous clinical trials. However, as sequencing technologies advance, what was once the stuff of science fiction is gradually becoming a 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 Centre, the Montreal Cancer Institute, the Mirella and Lino Saputo Foundation, Génome Québec and the Mitacs Foundation for research projects on liquid biopsy. He is a member of the Montreal Cancer Institute and a researcher at the CHUM Research Centre. He is named as an inventor on patents, some of which have been licensed for commercialisation by Eurofins-Viracor.
Tags: Academic Journalism, The Conversation, The Conversation Academic News
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