PARIS — Multicancer early detection blood (MCED) tests are the focus of intensive development. What techniques do these tests use? What potential do they show? Suzette Delaloge, MD, MSc, oncologist, breast cancer specialist, and director of the individualized cancer prevention program (Interception) at the Gustave Roussy Institute in Villejuif, France, looks into these "liquid biopsies" and shares her reservations about their potential marketing, especially to the organization of care plans.
Medscape: What are the general principles underpinning these MCED tests?
Suzette Delaloge, MD, MSc: Despite their specificities, the general idea is to detect certain cancer markers in various body fluids (blood, urine, saliva, etc.), for example, molecules released by cancer cells (cytokines, inflammatory proteins, leptin, etc.) or distinctive features of the DNA in tumor cells. In blood, these molecules can be found in plasma or in serum. In urine, it's more about detecting kidney, bladder, and urinary tract cancers.
Medscape: What sort of time frame are we looking at for these MCED tests to be used in routine practice?
Delaloge: They first appeared around 10 years ago. Development of these tests has intensified in recent years. There are numerous research laboratories, both public and private, that are developing different early-detection tests for cancer.
Some of these development processes are about to come to an end and are expected to be in regular, concrete use within 5-10 years. For the most advanced developments, the main biologic material researched and analyzed is DNA from cancer cells. We all have fragments of DNA from dead cells in our plasma (apoptosis), but cancer cells release more of these than others, and most importantly, their DNA has distinctive characteristics. The idea is to develop tests capable of detecting these characteristics.
Liquid biopsies based on genomic biomarkers could make MCED a reality, especially for cancers for which there is no standard screening process. But at this stage of the research, there are limitations, including low sensitivity for detecting stage I cancers in validation studies and an increased risk for overdiagnosis.
Medscape: What specific set of characteristics are the most advanced approaches based on?
Delaloge: They're based on the analysis of DNA methylation, a biological process by which CH3 methyl groups are added to the DNA molecule and that determines gene expression. This phenomenon differs depending on whether the cell is cancerous. Among the tests currently under development making use of this specific characteristic is the Galleri test, which is the most advanced of them all.
A previous British National Health Service (NHS) study, SYMPLIFY, which was published in 2023 by researchers at the University of Oxford, was conducted in symptomatic patients attending a health center [see box]. It offers promising results in a diagnostic situation. It has nothing at all to do with screening here. A large, randomized English study, NHS-Galleri, is underway, this time involving the general population, with the aim of assessing the potential benefit of the same test as screening in 140,000 people between ages 50 and 77 years.
Medscape: Does MCED testing concern all types of cancer?
Delaloge: The Galleri test is based on full profiling of DNA methylation. This allows for early diagnosis of cancer even before it can be seen on imaging tests. The issue with these tests is that they aren't that good at early diagnosis of the most common types of cancer (breast, colorectal, cervical, etc.) for which we already have more efficient means such as the fecal immunochemical test for colorectal cancer, mammography, HPV testing, and so on.
These blood tests would thus not be aimed at replacing routine screening but rather at screening asymptomatic individuals or those with nonspecific signs for cancers for which we have few or no screening measures and which are on the rise, such as deep tumors and cancer diagnosed at a late stage, namely pancreas, bile duct, ovarian, esophageal, lung, stomach, etc.
The results from the studies published are promising, but others are underway to confirm the benefit of these MCEDs. The challenge is to identify cancer at an early stage, at a stage where it will be easier to cure the patient and control its growth using treatments that are less onerous for the patient and that have fewer aftereffects but not at the expense of a massive increase in overdiagnosis, as seen with prostate-specific antigen levels in prostate cancer a few years ago!
Medscape: What would be the focus of these MCED tests?
Delaloge: We must be alert to the risk for the market development of MCED tests. For now, they are mostly, especially the Galleri test, developed in the general population to screen for types of cancer that could not be detected in any other way but also because it's the most financially beneficial situation. The designers want to position themselves in the general population, regardless of whether this means they'll have to test hundreds of people to find one for whom the test is beneficial. What's more, developing tests in isolation, without considering their place in ad hoc treatment pathways, is not realistic. It's likely that some of these tests will be marketed within the next 10 years, but the healthcare systems destined to receive them are not remotely ready to do so.
Medscape: An even more recent publication, from late July 2023, is even more exciting in relation to early detection of lung cancer using circulating DNA sequencing. What are your thoughts on it?
Delaloge: Initially overtaken by other technologies in favor of MCED approaches, DNA sequencing as a technique to detect somatic mutations seems to have reentered the competition with this new-generation research. The authors published some very interesting results, especially for stage I lung cancer with a very high sensitivity of 75%. [Editor's note: A machine-learning model using genome-wide mutational profiles combined with other features and followed by CT imaging detected more than 90% of patients with lung cancer, including those with stage I and II disease.]
This research illustrates the difficulty of providing high performance while covering a broad range of cancers. Here, the good results mainly concern lung cancer. Researchers and healthcare authorities must be alert to ensuring that MCED tests prove themselves in terms of sensitivity and specificity in responding to a medical need and in their impact on specific mortality. This craze for MCED tests must not hinder the development of "single-cancer" technologies that may be much better for detecting specific cancers. This recent publication is interesting in this respect, because this sequencing test seems to be particularly good at detecting lung cancer.
Medscape: Another approach used in MCED tests is based on analyzing the size of DNA fragments in the blood. Can you explain how this works?
Delaloge: When cancer is not present, the size of DNA fragments in cells is much more homogeneous. Here also, the benefit of MCED based on this technique rests on the very early detection of cancers that are less common than those for which we already have good screening methods available.
Other approaches, still at the experimental stage, detect certain proteins, certain inflammatory molecules, RNA, etc. But for many researchers, the future will involve pairing tests on the basis of circulating DNA in the blood with the detection of specific molecules indicating the presence of cancer to obtain early screening tests that are even more effective or that possibly even allow us to identify an appropriate treatment at an early stage.
The development of a simple test based on a blood draw that allows us to screen early for all cancers and that would replace all current screening measures is, therefore, not imminent, although it could potentially be on the horizon in years to come. Alongside this, an important issue is the benefit of cancer screening in the general population vs in a targeted population with a specific risk. The latter option is in development but requires an individualized screening pathway based on blood testing and current screening methods: imaging, etc. It also depends on an individual's cancer risk profile such as age, personal and family medical history, genetic predisposition, and so on.
This article was translated from the Medscape French Edition.
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Cite this: What Is the Future for Multicancer Early Detection Tests? - Medscape - Oct 03, 2023.