Inhaled corticosteroids and the risk of lung cancer in COPD: a population-based cohort study

Inhaled corticosteroids (ICSs) are often prescribed in patients with chronic obstructive pulmonary disease (COPD). Their impact on the risk of lung cancer, a leading cause of mortality in COPD patients, remains uncertain. Population-based linked administrative data between the years 1997 and 2007 from the province of British Columbia, Canada, were used to evaluate the association between lung cancer risk and ICS use in COPD patients. COPD was defined on the basis of receipt of three COPD-related prescriptions in subjects >= 50 years of age. Exposure to ICS was incorporated into multivariable Cox regression models using several time-dependent methods ("ever" exposure, cumulative duration of use, cumulative dose, weighted cumulative duration of use and weighted cumulative dose). There were 39 676 patients who met the inclusion criteria. The mean +/- SD age of the cohort was 70.7 +/- 11.1 years and 53% were female. There were 994 (2.5%) cases of lung cancer during follow-up. In the reference case analysis (time-dependent "ever" exposure), ICS exposure was associated with a 30% reduced risk of lung cancer (HR 0.70 (95% CI 0.61-0.80)). ICS exposure was associated with a decrease in the risk of lung cancer diagnosis over all five methods of quantifying exposure. This population-based study suggests that ICS use reduces the risk of lung cancer in COPD patients.