Launched by the Assistance Publique-Hôpitaux de Paris (AP-HP), the Cascade study (Lung cancer screening in French women by low-dose scanner) is delivering its first results a year later, and they are worrying for the smokers. A year ago, the High Authority for Health (HAS) recognized the value of such an approach. Some 3,000 women smokers or ex-voluntary smokers aged 50 to 74 have already contacted the authors of this pilot study funded by the Inca and the Ministry of Health and 1,300 have been integrated into it, 85% of whom are active smokers. .
Eventually, the cohort will be made up of 2,400 volunteers, twice as many women as in the mixed Nelson study published in 2020 of more than 15,000 volunteers but made up of an overwhelming majority of men. Detailed review of the first results with Pr Marie-Pierre Revel, head of the radiology department at Cochin Hospital, principal investigator of the Cascade study, still looking for volunteers.
Le Point: What are the first data from your study on the systematic screening of lung cancer in women?
Pr Marie-Pierre Revel: The study shows that the rate of positive tests is two to three times higher in women than in men. One CT scan out of thirty is positive in this study. This confirms in “real life” that, for equivalent tobacco exposure, a woman’s risk of developing lung cancer is much higher.
Did these numbers surprise you?
This is more than double what we expected. The Nelson study published in 2020, where men were in the majority (83%), showed a positive screening rate of 0.9%. Among women, we find in our study that the positive screening rate is between 2 and 3% one year after the start of the study. That’s more than double the male figure.
Why is a woman who smokes as much as a man has a higher risk of developing lung cancer?
There are several hypotheses. One of them is based on differences in body surface area. Between a woman who is 1.60 m for 50 kilos and a big guy of 1.85 m for 90 kilos, the airways obviously do not have the same surface. Probably, in women, the same quantity of smoke is therefore concentrated on a more restricted surface. We also know that addiction to tobacco is stronger in women. Hormones likely play a role in this difference. But there are no definite answers yet.
No way. We need to alert women smokers much more to the risks they run. Especially since the numbers are bad. While smoking is decreasing overall in France, it continues to increase among the female population. Nearly a quarter of French women smoke daily in 2021, an increase of 2% compared to 2019, according to data from Respadd, the addiction prevention network.
The share of women among those affected by lung cancer in France has increased from 16% in 2000 to 34.6% in 2020, according to data from general hospitals (KBP 2020) published in the Lancet Regional Health. In France, in the 1970s, lung cancer in women was an exception. Today, it has probably become the leading cause of cancer death in women, as is already the case in Europe.
Is the benefit of screening greater for women than for men?
This is important information to point out. Screening can reduce the risk of death from lung cancer, and this is even more true if you are a woman. For example, after a ten-year follow-up, the authors of the Nelson study report a decrease in lung cancer mortality of 26% in men and 33% in women.
Why in all the screening studies, are they more beneficiaries than men?
This is because they tend to develop a particular form of cancer, adenocarcinomas. These are less aggressive cancers than other tumors. Their growth is a little slower and this makes it possible to carry out screening which often makes it possible to start surgical treatment before the disease is too advanced.
Why do they suffer from these particular tumors?
It’s probably related to their smoking pattern. Cigarette and tobacco consumption habits changed in the 1960s and 1970s. Brown tobacco, without a filter, gradually gave way to so-called “light” cigarettes. The arrival of women in smoking coincided with the development of these new products with targeted marketing. But the inhalation of smoke is not the same depending on the type of cigarettes used.
With brown or unfiltered tobacco, you don’t need to inhale the smoke very deeply to get your nicotine fix. The smoke is therefore concentrated in the initial part of the respiratory tract, lined with a particular epithelium where a type of cancer that is also particular and often aggressive develops, squamous cell carcinoma. Men have been and are still more affected by these cancers. Conversely, so-called “light” cigarettes – often adopted by women early on – require the smoke to be inhaled deeply, causing it to concentrate in areas with different epithelium and resulting in different cancers, adenocarcinomas.
What are the next steps in your study?
We still need to recruit volunteers in Paris, Béthune, Grenoble and Rennes. They must be women between the ages of 50 and 74, smokers or former smokers (the equivalent of a pack a day for twenty years), without any symptoms. This last point is important to avoid bias in our study. This is also why we do not recruit through general practitioners. Moreover, after reading these initial results, the women concerned should not systematically be prescribed a chest scanner. Screening must be done in a specific setting with a scanner exposing them to low doses of radiation.
Your study also assesses the contribution of artificial intelligence (AI) in screening. Does it really make a difference?
All scans performed in the study are read twice, by the radiologist assisted by artificial intelligence and then by two experts. At this point, we can’t yet say that AI trumps double reading, but we can hope so! Indeed, in the event of generalization of screening, this would free up significant human resources.
Isn’t there a risk of false positives, i.e. of detecting a cancer which is ultimately not a cancer?
No, the fear of “false positives” has become a “false problem” because we know how to sort it out. None of these patients underwent invasive procedures, such as a biopsy or an unjustified operation.
What do you offer these women smokers?
We offer them systematic weaning assistance. 75% accepted it, because a majority want to quit smoking. Getting tested in time and getting help in the process of quitting smoking is the winning duo offered to Cascade participants.
IMPORTANT: To participate, contact 06 15 06 58 35 or cascade.cch@aphp.fr