Chronic obstructive pulmonary disease and cancer risk: a Danish nationwide cohort study.

INTRODUCTION Little is known about the risk of cancer in patients with chronic obstructive pulmonary disease (COPD), including which cancer sites are most affected. We examined the short- and long-term risk of lung and extrapulmonary cancer in a nationwide cohort of COPD patients. METHODS We linked the Danish National Registry of Patients and the nationwide cancer registry, and examined the incidence of various cancers in 236,494 individuals with a first incident hospital contact with COPD during 1980-2008. The observed cancer incidence in this cohort was compared with the expected incidence in the general population on the basis of national age-, sex-, and site-specific incidence rates. RESULTS Median follow-up was 3.5 years. During the first year of follow-up, 9434 cancers were diagnosed in COPD patients [standardized incidence ratio (SIR) = 3.1; 95% CI 3.0 to 3.2]. The 1-year SIR was 8.5 (8.2-8.9) for lung cancer, 5.1 (5.0-5.2) for all tobacco-related cancers, and 1.9 (1.9-2.0) for other cancers. In the following years, cancer incidence was increased 1.4-fold (1.4-1.5) in COPD patients. These patients had an increased risk of developing tobacco-related cancers (SIR = 2.1; 95% CI 2.0-2.1), including cancers of the lung, larynx, tongue, oral cavity, pharynx, esophagus, stomach, liver, pancreas, cervix uteri, and urinary tract (with SIRs ranging between 1.3 and 2.8). CONCLUSIONS Patients with first-time hospital-diagnosed COPD are at considerably increased risk of developing both lung cancer and extrapulmonary cancers. Physicians should be aware of cancer in COPD patients.