Chronic lung disease may increase the risk of developing lung cancer, independently of tobacco use and other known risk factors.
Epidemiologists in Europe and Canada have pooled resources to identify a relationship between respiratory disease and the risk of lung cancer.
In the study
, published August 15, 2014, in the American Journal of Respiratory and Critical Care Medicine
, investigators combined data from 7 studies conducted in Europe and Canada, including data from 12,739 patients with lung cancer and 14,945 control patients without lung cancer. Researchers analyzed the relationship between lung cancer and several conditions, including chronic bronchitis, emphysema, tuberculosis, pneumonia, and asthma.
To isolate the effect of chronic lung disease on the risk of developing cancer, investigators adjusted for several factors, including each patient's age, occupation, smoking status, and smoking history. Investigators matched patients with similar risk factors to compensate for these confounders using a stratified analysis.
With these adjustments, investigators found that chronic bronchitis increased the risk of developing lung cancer by 33% (95% CI: 20%–48%), and that emphysema increased the risk of developing lung cancer by 50% (95% CI: 21%–87%).
Moreover, patients with 3 concurrent lung conditions—chronic bronchitis, emphysema, and pneumonia—had the highest risk of developing lung cancer of any patient type, suggesting a synergistic inflammatory effect.
One chronic respiratory condition, asthma, may have a protective effect against lung cancer. Patients in the study with a minimum of a 5-year history of asthma were less likely to develop lung cancer than patients without asthma, although the finding was statistically insignificant.
The increase in the risk of developing lung cancer in patients with more than 1 type of lung disease that remained significant even after adjusting for prior tobacco use, suggest an inflammatory mechanism behind the development of lung cancer. These findings may lead to an improved understanding of the disease processes leading to lung cancer, potentially leading to new therapeutic modalities for at-risk groups.
Denholm R, Schüz J, Straif K, et al. Is previous respiratory disease a risk factor for lung cancer?. Am J Respir Crit Care Med
. Published online July 15, 2014.