Purpose: The goal of this study was to compare the risk of developing cancer between patients with or without chronic obstructive pulmonary disease (COPD), and to assess the role of gender as well as the use of respiratory medication on the risk of developing lung cancer in COPD patients.
Patients and methods: We used the UK-based General Practice Research Database to conduct a follow-up study with a nested case-control analysis. We identified all patients with a first-time COPD diagnosis aged 40-79 years between 1995 and 2005 and a matched COPD-free comparison group. We then identified all patients who received an incident cancer diagnosis during follow-up.
Results: Among 35,772 COPD patients and 35,772 COPD-free patients, we identified 4506 patients with an incident cancer diagnosis, of whom 2585 (57.4%) had a previous COPD diagnosis, yielding a crude incidence rate ratio of 1.64 (95% CI 1.55-1.74). The increased risk was mainly driven by a high lung cancer risk among COPD patients, while other cancers not associated with smoking were not statistically significantly associated with an altered COPD risk. In the nested case-control analysis, the odds ratio (OR) for lung cancer associated with COPD was higher for women (OR 5.26, 95% CI 3.64-7.61) than for men (OR 2.10, 95% CI 1.70-2.60). In the nested case-control analysis, none of the respiratory drugs were associated with a substantially altered risk of developing lung cancer among COPD patients.
Conclusion: Our findings provide further evidence that COPD is associated with an elevated lung cancer risk, and that women with COPD may be more susceptible to developing lung cancer than men. Overall, respiratory medication did not have an influence on cancer risk.
Keywords: COPD; GPRD; cancer; gender.