Incidence and relative risk for developing cancer among patients with COPD: a nationwide cohort study in Taiwan

OBJECTIVES This observational study aimed to examine the incidence of malignant diseases, including specific cancer types, after the diagnosis of chronic obstructive pulmonary disease (COPD) in Taiwanese patients. SETTING Taiwan's National Health Insurance Research Database. PARTICIPANTS The definition of a patient with COPD was a patient with a discharge diagnosis of COPD or at least 3 ambulatory visits for COPD. The index date was the date of the first COPD diagnosis. Patients with a history of malignancy disorders before the index date were excluded. After matching age and gender, 13 289 patients with COPD and 26 578 control participants without COPD were retrieved and analysed. They were followed from the index date to malignancy diagnosis, death or the end of study follow-up (31 December 2011), whichever came first. PRIMARY OUTCOME MEASURES Patients were diagnosed with cancer (n=1681, 4.2%; 973 (7.3%) for patients with COPD and 728 (2.7%) for patients without COPD). The risk of 7 major cancer types, including lung, liver, colorectal, breast, prostate, stomach and oesophagus, between patients with COPD and patients without COPD was also estimated. RESULTS The mean age of all study participants was 57.9±13.5 years. The average length of follow-up to cancer incidence was 3.9 years for patients with COPD and 5.0 years for patients without COPD (p<0.01). Patients with COPD were diagnosed with cancer (n=973, 73%) at a significantly higher rate than patients without COPD (n=708, 2.7%; p<0.01). The HR for developing cancer in patients with COPD was 2.8 (95% CI 2.6 to 3.1) compared with patients without COPD after adjusting for age, sex and comorbidities. The most common cancers in patients with COPD include lung, liver, colorectal, breast, prostate and stomach cancers. CONCLUSIONS The risk of developing cancer is higher in patients with COPD compared with patients without COPD. Cancer screening is warranted in patients with COPD.