Could COPD represent an independent risk factor for lung cancer?
Results of a new cohort study suggest that non-smokers with chronic obstructive pulmonary disease (COPD) are at a heightened risk of developing lung cancer compared with non-smokers without COPD.
Much research has demonstrated that individuals with chronic obstructive pulmonary disease (COPD) who have histories of smoking face heightened risks of developing lung cancer; less research has investigated if this risk is similarly greater for individuals with COPD who have never smoked. Now, new research, led by investigators from the Sungkyunkwan University School of Medicine (Seoul, South Korea), suggests that non-smokers with chronic obstructive pulmonary disease (COPD) may be over 2.5 times more likely to develop lung cancer compared with non-smokers without COPD.
Smoking is the primary risk factor for COPD – a term that encompasses acute respiratory conditions such as bronchitis and emphysema – and is also a known risk factor for the development of lung cancer. However, an estimated 39% of individuals with COPD are non-smokers.
In this study, researchers employed data from the National Health Insurance Service National Sample Cohort study (Seoul, South Korea); a total of 338,548 individuals (43% men), aged 40—84 years with no histories of lung cancer, were included in the study. Study participants' health was tracked for a median 7 years, utilizing prescription filling data and inpatient and outpatient treatment information.
Over the course of the study period there were 1834 new cases of lung cancer reported; 1544 cases were in individuals without COPD and in 290 cases, the subject had COPD. Participants with COPD were more likely to be male, older and have additional comorbidities.
Further analysis, stratifying study participants according to their histories of smoking, revealed that those with COPD who smoked were six times more likely to develop lung cancer compared with non-smokers who did not have COPD.
Smokers who did not have COPD were twice as likely to develop lung cancer compared individuals who did not have COPD and did not smoke.
Further, amongst study participants who had never smoked, the incidence of lung cancer was more than 2.5 times greater amongst those with COPD compared with individuals who did not have COPD; this risk level for lung cancer development was similar to that of smokers who did not have COPD.
In the study, the authors note: “Given that poor lung function in COPD is often a barrier to optimal lung cancer treatment, due to increased risk of treatment-related morbidities, our study suggests that early detection of lung cancer in COPD patients may reduce the risk of treatment complications.”
Important limitations of the study include that the researchers did not assess severity of COPD in the study, nor was information on participants environmental and occupational exposures to elements associated with increased risk of lung cancer available to them.
Nevertheless, the authors concluded: “…COPD was a strong independent risk factor for lung cancer incidence in never smokers…never smokers with COPD had a similar risk of lung cancer compared with ever smokers without COPD.”
“Patients with COPD are at a high risk of lung cancer and future studies should evaluate whether COPD patients are candidates for lung cancer screening, irrespective of smoking status.”
Park HY, Kang D, Shin SH et al. Chronic obstructive pulmonary disease and lung cancer incidence in never smokers: a cohort study. Thorax. doi:10.1136/thoraxjnl-2019-213732 (2020) (Epub ahead of print)