Association between short-term cumulative exposure to PM2.5 and lung cancer

Recent air pollution exposure in the form of particles smaller than 2.5 micrometers exposure may significantly impact lung cancer in women who have never smoked, with notable differences in stage IV diagnoses among EGFR+ patients.

Exposure to air pollutants has long been known to predispose to various respiratory diseases. Small air pollutants such as particles smaller than 2.5 micrometers (PM_2.5) allow invasion deep into the airways and lung tissue. It has been suggested that exposure to PM_2.5 is a risk factor for lung cancer, possibly due to activation of various signalling pathways. However, the timing and duration of PM_2.5 exposure with particular relevance to lung cancer is not well characterised. Therefore, Dr. Chen et al. set up a study to compare the associations between recent versus long-term cumulative PM2.5 exposure in men and women who had never smoked and lung cancer EGFR mutation status.

Study design

This study aimed to compare associations between short- vs. long-term exposure to PM_2.5 before diagnosis and genomic alterations in non-smokers using logistic regression models. Non-smokers presenting to the British Columbia Cancer Institute with newly-diagnosed lung cancer completed a questionnaire including residential history from birth until diagnosis. Each residential area was geo-coded and high-resolution concentration estimates of PM_2.5, chemical transport models, and ground measurements within a 10x10km area were analysed. Annual exposure data was obtained going back to 1996 when accurate air pollution information became available globally.

Results

A total of 255 participants with known EGFR mutation status were included in the analysis. A significant association between EGFR mutation and cancer stage was found among women (p=0.197 in males, p<0.001 in females). Patients diagnosed with stage IV lung cancer displayed higher proportions of EGFR mutations compared to those without.  Further associations for PM_2.5 exposure in the year prior to diagnosis in female non-smokers with EGFR mutations compared to those without were also found (6.4 vs. 6.1µg/m³, p=0.003). This trend also persisted for long-term exposure prior to diagnosis (3-year: 19.0 vs. 17.3µg/m³, p= 0.031; 5-year: 33.7 vs. 29.5 µg/m³, p= 0.024), with higher exposure observed in the EGFR-mutation positive group. This association was not noted in males who never smoked. Interestingly, PM_2.5 exposure was higher long prior to diagnosis, particularly 10 to 15 years prior, however, long-term exposure was not associated with EGFR mutation status.

Conclusion

The results of this study may suggest an association between PM_2.5 on lung cancer stage in female non-smokers. Further studies are required to determine if PM_2.5 levels over a 3 or 5-year period is sufficient for lung cancer risk assessment.

Reference

Chen YC, et al. PM2.5 exposure impact on never smoking lung cancer patients. Presented at WCLC 2024; Abstract 3146.