Efficacy of lower dose pirfenidone for idiopathic pulmonary fibrosis in real practice: a retrospective cohort study

Background/Aims: Pirfenidone slows the progression of idiopathic pulmonary fibrosis (IPF). We investigated its efficacy and safety in terms of dose and disease severity in real-world patients with IPF. Methods: This multicenter retrospective cohort study investigated 338 patients treated with pirfenidone between July 2012 and March 2018. Demographics, pulmonary function, mortality, and pirfenidone-related adverse events were also investigated. Efficacy was analyzed according to pirfenidone dose and disease severity using linear mixed-effects models to assess the annual decline rate of forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO). Results: The mean %FVCpredicted and %DLCOpredicted values were 72.6% +/- 13.1% and 61.4% +/- 17.9%, respectively. The mean duration of pirfenidone treatment was 16.1 +/- 9.0 months. In the standard dose (1,800 mg/day) group, the mean %FVCpredicted was -6.56% (95% confidence interval [CI], -9.26 to -3.87) per year before, but -4.43% (95% CI, -5.87 to -3.00) per year after treatment with pirfenidone. In the non-standard lower dose group, the mean %FVCpredicted was -4.96% (95% CI, -6.82 to -3.09) per year before, but -1.79% (95% CI, -2.75 to -0.83) per year after treatment with pirfenidone. The FVC decline rate was significantly reduced, regardless of the Gender-Age-Physiology (GAP) stage. Adverse events and mortality were similar across dose groups; however, they were more frequent in GAP stages II-III than in the stage I group. Conclusions: The effect of pirfenidone on reducing disease progression of IPF persisted even with a consistently lower dose of pirfenidone.