COPD Seen to Raise Risk of Lung Cancer in Non-smokers

Chronic obstructive pulmonary disease (COPD) is linked to a higher risk of lung cancer in people who never smoked. In fact, their risk is equivalent to current or former smokers who do not have COPD, a research team reports.

The study, “Chronic obstructive pulmonary disease and lung cancer incidence in never smokers: a cohort study,” was published in the journal Thorax.

Smoking is the major risk factor for COPD, and is itself associated with a higher likelihood of lung cancer. COPD is also often associated with disorders that include lung cancer, but the link between COPD and lung cancer among people who have never smoked is unclear.

“While up to 39% of COPD patients are never smokers, there is very limited evidence on the association between COPD and lung cancer incidence in this group, as most studies used cross-sectional or case-control designs and included relatively few never smokers,” the researchers wrote.

To explore a possible association, investigators in South Korea in collaboration with those in the U.S. analyzed data from a large group of Korean citizens. They examined the incidence and estimated the risk of lung cancer among smokers and non-smokers with and without COPD.

Data was extracted from the National Health Insurance Service – National Sample Cohort (NHIS-NSC), a population-based cohort study, between January 2002 and December 2013. In total, information covered 338,548 individuals of both sexes, ages 40–84, with no history of lung cancer.

During a median follow-up of seven years, 1,834 of these people developed lung cancer. Among them, 290 also had COPD, while 1,544 did not.

Statistical analyses revealed that compared to non-smokers without COPD, non-smokers with COPD were 2.67 times more likely to develop lung cancer.

Analyses showed that current and former smokers without COPD also had a lung cancer risk nearly twice that of non-smokers without COPD. This risk increased to more than six times in individuals who had COPD and were either current or former smokers.

“Interestingly, the risk of lung cancer development in never smokers with COPD was similar to the risk observed in ever smokers without COPD,” the researchers wrote.

“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,” they added.

This study had limitations that could be sources of bias in its results, including a lack of information regarding COPD severity and about exposure to certain environmental risk factors. Still, its investigators believe their findings demonstrate that COPD is “a strong independent risk factor for lung cancer incidence in never smokers.”

“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,” the team suggested.