Lung Function Course of Patients With Pulmonary Fibrosis After Initiation of Anti-Fibrotic Treatment: Real-World Data From the Dutch National Registry

Background and Objective: Real-world data on lung function course of patients with progressive pulmonary fibrosis (PPF) treated with anti-fibrotic medication are limited. We evaluated forced vital capacity (FVC) decline in patients with PPF and idiopathic pulmonary fibrosis (IPF) who started anti-fibrotic treatment. Methods: This was a nationwide multi-centre registry study in 16 hospitals throughout the Netherlands. Patients treated with anti-fibrotic medication, with at least two in-hospital pulmonary function tests before and after the initiation of anti-fibrotic treatment, were included. Linear mixed-effects modelling was used to analyse lung function trajectories 1 year before and after the start of anti-fibrotic treatment. Results: Data from 538 patients (n = 142 with PPF, n = 396 with IPF) were analysed. In PPF, the mean annualised FVC decline was 412 mL (95% confidence interval [CI]: 308–517 mL) before the initiation of anti-fibrotic treatment, and 18 mL (95% CI: 9–124 mL) in the first year after. The corresponding declines for IPF were 158 mL (95% CI: 78–239 mL) and 38 mL (95% CI: 24–101 mL). In both groups, treatment significantly slowed down FVC decline, although the change was larger in the PPF group (p = 0.0006). In the first year after treatment initiation, 23.9% of patients with PPF and 28.0% with IPF had disease progression. Conclusion: The FVC decline significantly slowed after the initiation of treatment for both IPF and PPF. Nevertheless, a significant proportion of patients exhibited disease progression, despite the start of anti-fibrotic treatment. Early identification of these patients is crucial for treatment adaptations and inclusion in clinical trials.