Difficult to carry out your boat, when, to face the storm, you have no meteorological survey and thumbs down on the mat. The analogy is also true for early cancers: until very recently, France had no follow -up on the number of these malignant tumors which affect those under 40. When they existed, the files were left at the bottom of the drawers, for lack of centralization.
The institutions of the country thus found themselves very devoid, when, in 2023, some scientists began to alert to a possible “epidemic” of these diseases on a global scale. While abroad several curves were flying away, French specialists were reduced to the simple critical commentary on the potential biases of the work of their colleagues. Impossible, therefore, to invalidate or confirm these theses or to say to what extent France was, or not, also concerned.
Two years later, and while many media have echoed in recent months of the alleged peril, France finally has statistics. Frustrated with not being able to use this type of data, a scientist of the national register of the solid tumors of the child, Dr. Emmanuel Desandes, decided to carry out his own work, with his team. He finally obtained funding from the League against Cancer, and supported him from the National Cancer Institute (INCA) and Public health France.
The conclusions of his study, Presented Monday March 3do not give a complete vision of the situation. The curves thus drawn are in reality partial and subject to many biases: “In the absence of centralization, only 19 departments had a continuous register and scientific standards. The results concern only 18 % of the territory, and it is not possible to extrapolate them”, warns the author. But this work at least helps dissipate part of the thick fog in which researchers were sailing so far.
No tsunami or epidemic, but …
First observation: the tidal raz mentioned by some scientists did not take place in our country, at least not yet. Cancers remain rare in this age group. In 20 years, 21,628 cases have been identified in men, and 33,107 in women, less than 3,000 cases per year, on average. By way of comparison, in 2024, 430,000 cases of cancer were detected all ages combined in France, according to the Inca figures, which enaches a national representative assessment each year for those over 40.
Above all, no “epidemic” seems to work: “There has never been a serious scientific controversy on the subject,” insists Claire Morgand, director of data science observation and ENCA assessment. If the incidence of cancers in those under 40 first “increased by 1.62 % per year between 2000 and 2014”, date of start of the statements, it then “fell 0.79 % per year between 2015 and 2020”, summarized Public Health France, in a press release. On average, early tumors have therefore been less frequent over the most recent period in the departments studied.
The dynamics could even be even better than announced: “In some cases, changes in the classification of these tumors occurred during this period, and the improvement of the molecular diagnosis, in connection with diagnostic practices, could have an impact,” said Emmanuel Desands. In other words, improving diagnostic techniques and changes in the methodology have been able to mechanically increase a number of indicators. This is at least what happened in the field of cancers of the nervous system, up in the study, still according to Public Health France.
… Six cancer constantly increasing
The general decline in early cancers in young people highlights the effects of prevention, intense in recent years. This is in particular the main explanation mentioned by the authors to explain the decline in melanoma, skin cancer emblematic skin exposure habits, down 3 % per year since 2010. “In 1990, nobody knew that it was necessary to avoid these tumors, you had Ultraviolet cabins on every street corner. Today, there is not a child on the beach which does not have its combination, Director of Research at the League against Cancer.
The fact remains that, in detail, the study also emerges several alert points, already more or less known to scientists. Researchers point out that six types of tumors have a constant and significant increase since the 2000s: colorectal carcinomas (+ 1.43 %per year), breast (+ 1.6 %), kidney (+ 4.51 %), Hodgkin lymphomas (+ 1.86 %), glioblastomas (+ 6.11 %) and liposarcoma (++ 3.68 %). “These dynamics ask to be confirmed by other studies and have nothing of an epidemic. But that justifies that we are interested in it, and if we detect a substantive trend, that we are looking for explanations,” nuances Dr. Emmanuel Desandes.
The trends thus underlined are fragile, because by definition early cancers are not frequent enough to produce without appeal conclusions. The increase in glioblastomas and liposarcomas can for example appear important, but it actually relates only to a few cases. There was, in all and for everything, 233 cases and 145 cases detected of these types of cancer, over the period 2000-2020, or less than 12 cases per year on 19 departments. With such limited data, the slightest change may seem more important which is really.
The difficulty of interpreting studies
What is more, observing an increase in cases, even when it is confirmed, is not enough to demonstrate that the risk of having cancer is more important. It could just as much be a statistical illusion, linked to isolated events. “To decide, it would be necessary to separate men and women, who are not equal in the face of cancer, to look at the statistics in the older population, to know if the problem is specific, and to look if the dead increase, to eliminate the biases linked to screening. It is much more work,” recalls Catherine Hill, epidemiologist at the Gustave-Roussy Institute, Villejuif (Val-de-Marne).
However, some trajectories seem to be confirmed. Like that of breast cancers, the increase of which is known and strong in all age groups, and particularly marked in France. This dynamic is partly explained by the progression of smoking and alcohol consumption, although other hypotheses are also being studied such as hormone taking or exposure to endocrine disruptors, more and more evoked in the scientific literature.
The study of Dr. Desands also seems to go in the direction of an increase in colorectal cancers and the kidney, although it is not specific to young people. Many countries seem concerned by this trend, whose scientists still struggle to understand the causes. “The explanation could be in the increase in obesity. More and more studies go in this direction, but, as always in cancer, the risk factors are multiple and entangled, which makes research particularly complex,” continues Iris Pauporté.
These new data should feed future research in this area. Last year, the Gustave-Roussy cancer center launched a large survey called Yodawhich focuses on possible environmental factors that can promote the appearance of digestive tumors in young people. The National Institute of Cancer and Public Health France also announced to L’Express embarking on more in -depth analyzes on glioblastomas, in order to verify whether the increase observed is very significant.
These studies should thus provide reliable information to the population. Convinced that an explosion of cases would end up appearing in France, many newspapers have devoted some to the phenomenon, on the basis of studies carried out abroad. Even if it means relaying unfounded hypotheses, and to portray an agonizing situation far from reality, as Jacques Robert recently denounced, professor emeritus of cancerology at the University of Bordeaux and former president of the French Cancer Society.
An “80 % increase in cancers in those under 50”, really?
Among these international productions taken up without much decline, one particularly marked the spirits. Published in the British Medical Journal In 2023, this analysis reported an increase of “80 % of cases in those under 50” around the world. Since then, the figure continues to be repeated. However, it is in no way useful. “Only the standardized impact rate by age makes it possible to account for the trend. Expressed in number of cases, the results are too sensitive to the dynamics of increased population, and are subject to huge biases,” said Catherine Hill.
These debates have at least had the merit of highlighting the need for a real surveillance program. In 2023, a bill was voted in this sense by the Senate, at first reading. A dissolution and three governments later, the provision does not appear in the priorities of the National Assembly. It is not unanimous among scientists: “exhaustive follow -up would cost tens of millions of euros. We could use the existing registers and consolidate them with other sources available to draw representative indicators”, offers Claire Morgand, to Inca. What, in one way or another, to light our vision of these pathologies a little more.
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