If the technology is not yet very reliable and is very expensive, doctors are enthusiastic about being able to identify tumors even before they are visible.
( AFP / PATRICK HERTZOG )
Identifying a tumor early in the body, gauging the effectiveness of a treatment or even monitoring the evolution of the disease… All of this should one day be possible thanks to simple blood tests, believes the scientific community.
A better understanding of the mechanisms associated with the disease and recent technological advances have made it possible to make giant strides in this field. Dozens of studies are underway to demonstrate the usefulness of using a new tool, “liquid biopsy”, in monitoring patients treated for cancer.
A liquid biopsy is simply a blood test that aims to
to search the blood of a patient for fragments of DNA from the tumor
or cancer cells. This technique has considerable advantages and many observers believe that its discovery would deserve a Nobel Prize in medicine: it is notably much less invasive than a “classic” biopsy, which takes tissue from the body.
Above all, it contains very precise information on a patient’s cancer: “The sampling of what is called
‘circulating DNA’ aims to detect mutations
for certain types of cancer, and thus adapt the treatments accordingly”, explains Alain Thierry, research director at the Cancer Research Institute of Montpellier, a specialist in the subject. For certain cancers such as those of the lung, where the tumors are often difficult to access, this is real progress.
The analysis of the blood of patients could also soon make it possible to monitor how a cancer reacts to treatment. “In concrete terms, after the surgical removal of a tumour, chemotherapy is often prescribed when we do not know if the patient really needs it”, notes Alain Thierry. In the future, the analysis of a patient’s blood may, in many cases, make it possible to
administer less heavy or less long treatments but also detect possible recurrences.
Early detection
But the liquid biopsy also conceals other potentials, certainly much more uncertain. “There is one that is dizzying: it is the early detection of cancer”, enthuses Alain Thierry. Several teams and biotechs are working on it around the world. The idea: to be able to detect a tumor in an individual by taking a blood sample, even before symptoms appear or it is visible on an X-ray.
“Technologically, it is much more complicated than cancer monitoring because it requires large-scale analysis of DNA mutations but also other specific markers, while not knowing in advance what we are looking for”, describes François-Clément Bidard, oncologist at the Curie Institute, head of the laboratory of circulating tumor biomarkers.
Recently, the results of a study by the American biotech Grail have been particularly noticed. In their trial, a blood sample was taken to
detect cancers in individuals aged 50 and over who are a priori healthy
. More than 6,600 people took the test. There was a suspicion of cancer for 92 of them. In the end, 35 actually had confirmed cancer during the year and 57 people therefore mistakenly believed that they had one. But the test made it possible to detect 9 cancers which would probably not have been detected by early conventional screening.
Mixed results
However, the results are very mixed.
and it will likely take years to improve the reliability of these tests, which are already marketed in the United States.
And, even reliable, these tests will still raise certain questions, warns François-Clément Bidard. “One of them is the cost, this type of sequencing being extremely expensive. Another subject is the possible ‘over-diagnosis’ induced by these tests, because a certain number of cancers detected have in fact an extremely slow evolution. and do not necessarily require treatment,” he explains.
It will also be necessary to prove that these tests represent a notable progress compared to those which are in force today.
“We still have well-established cancer screening strategies today”
but “the participation rate is only 40% at best” in these screening tests offered by Health Insurance, recalls Professor Fabrice Barlesi, director general of the Gustave-Roussy anti-cancer center, who does not however exclude not that blood tests are ever used as a “complement”.
