Lung Cancer Risk Among Patients with Asthma-Chronic Obstructive Pulmonary Disease Overlap.

RATIONALE Chronic obstructive pulmonary disease (COPD) is a well-established independent risk factor for lung cancer, while the literature on the association between asthma and lung cancer is mixed. Whether Asthma COPD Overlap (ACO) is associated with lung cancer has not been studied. OBJECTIVES We aimed to compare lung cancer risk among patients with ACO vs. COPD and other conditions associated with airway obstruction. METHODS We studied 13,939 smokers from the National Lung Cancer Screening Trial who had baseline spirometry, and utilized spirometric indices and history of childhood asthma to categorize participants into 5 specific airway disease subgroups. We used Poisson regression to compare unadjusted and adjusted lung cancer risk. RESULTS The incidence rate of lung cancer per 1,000 person-years was: ACO, 13.2 (95% confidence interval [CI]: 8.1-21.5); COPD, 11.7 (95% CI: 10.5-13.1); asthmatic smokers, 1.8 (95% CI: 0.6-5.4); Global Initiative for Chronic Obstructive Lung Disease-Unclassified, 7.7 (95% CI: 6.4-9.2); and normal-spirometry smokers, 4.1 (95% CI: 3.5-4.8). ACO patients had increased adjusted risk of lung cancer compared to patients with asthma (incidence rate ratio [IRR]: 4.5, 95% CI: 1.3-15.8) and normal spirometry smokers (IRR: 2.3, 95% CI: 1.3-4.2) in models adjusting for other risk factors. Adjusted lung cancer incidence in patients with ACO and COPD were not found to be different (IRR: 1.2, 95% CI 0.7 - 2.1). CONCLUSIONS Risk of lung cancer among patients with ACO is similar to those with COPD and higher than other groups of smokers. These results provide further evidence that COPD, with or without a history of childhood asthma, is an independent risk factor for lung cancer.