DENVER — Asthma may be a risk factor for lung cancer, according to two new meta-analyses.
The public health implications of such an association would be enormous. Asthma affects at least 15 million Americans, 40% of them children. Its prevalence has been climbing steadily for decades in developed countries, more than doubling in the United States during a recent 20-year period. And lung cancer is the second most common noncutaneous malignancy in this country, with 10% of lung cancer deaths not attributable to smoking, Chanis Mercado said at the annual meeting of the American Public Health Association.
One of the two meta-analyses she performed as a Ph.D. candidate in public health at the Ponce (P.R.) School of Medicine involved 17 high-quality case-control studies with a total of 54,238 subjects. The conclusion was that individuals with asthma had 34% greater odds of having lung cancer, compared with matched controls without asthma.
A separate meta-analysis that included 16 high-quality cohort studies and 1,384,824 subjects showed that those with asthma were 46% more likely to develop lung cancer than were subjects without asthma.
These results were statistically robust. Eliminating any individual study didn’t substantially change the results. Tests for the existence of publication bias proved reassuringly negative.
One biologically plausible possible mechanism for the observed asthma–lung cancer link is that the persistent chronic inflammation that is a defining feature of asthma causes DNA damage to cells in the airway. Another possibility is that asthma patients have defective clearance of toxins in the bronchioalveolar epithelium, resulting in prolonged local exposure to carcinogens, she said.
The clinical implication of these two meta-analyses is that asthma patients ought to be screened earlier and more often for signs and symptoms of lung cancer, Ms. Mercado continued. This screening might take the form of chest x-rays, sputum cytology tests, and/or a low threshold for acting on symptoms of weight loss or hemoptysis.
Ms. Mercado declared having no relevant financial interests.