2024-01-25 18:05:56
One in ten lung cancer is not caused by tobacco. And these bronchopulmonary cancers occurring in individuals who have never smoked are progressing. For example, in France, 12.6% of lung cancers were of “non-smoking” origin in 2020 compared to 7.2% in 2000. The main risk factor for these cancers is air pollution.
Fine particles and lung cancer: a link demonstrated only since 2023
Established by a decisive English study in 2023, this relationship between atmospheric pollution (fine particles, in particular those with a diameter less than 2.5 μm/PM2.5) and the occurrence of bronchopulmonary cancers in non-smokers carrying mutations in the EGFR gene (other mutations exist) is now demonstrated.
The fine particles would “activate” certain pre-existing genetic mutations in the healthy lung, thus transforming a normal lung cell into a cancer cell. One of the most frequent mutations concerns the gene for a key protein: EGFR (epidermal growth factor receptor). However, this mutation is present in 50% of bronchopulmonary tumors in non-smokers, and less than 5% in smokers.
The new French figures
In the French KBP-2020 study, for one year, all diagnosed cases of lung cancer as well as the genetic characteristics of the patients were collected. “ This was an opportunity to study the impact of pollution on lung cancer in order to confirm the results obtained by the London research team led by Charles Swanton.indicates Professor Alexis Cortot, pulmonologist at Lille University Hospital and coordinator of the study.
For its third edition, KBP included approximately 9,000 patients. Each city of residence of the patients was associated with a level of exposure to different pollutants such as PM2.5, PM10, ozone, nitrogen dioxide, ionizing radiation (radon). Mutations favoring cancers were searched for (EGFR, ALK, ROS, KRAS, etc.). The results show that there is indeed a link between exposure to fine PM2.5 particles and the proportion of EGFR mutations among diagnosed lung cancers, with a risk equal to 1.5.
Therefore, patients residing in polluted areas have a 50% increased risk of having lung cancer with this type of mutation. This level of risk is similar to that associated with passive smoking and fifteen times lower than that of active smoking. The presence of EGFR mutations has been associated not only with PM2.5, but also PM10 and nitrogen dioxide.
The pro-inflammatory effect of fine particles
In this relationship between exposure to fine PM2.5 particles and the development of “EGFR mutated” bronchial cancer, scientists have highlighted the involvement of inflammation. There is a pro-inflammatory effect of exposure to PM2.5. Thus, these pollutants trigger an inflammatory reaction which promotes the development of lung cells which harbor potentially cancerous (“oncogenic”) mutations in EGFR, and which are present in approximately 15-20% of healthy subjects.
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