Progressive Fibrosing Interstitial Lung Diseases: Prevalence and Characterization in Two Italian Referral Centers

Background: The prevalence and natural history of progressive fibrosing interstitial lung diseases (PF-ILDs), and their response to commonly used treatments in real life are largely unknown. Objectives: The aim of the study was to describe the prevalence, clinical characteristics, management, and outcomes of PF-ILD patients attending 2 Italian referral centers (San Gerardo Hospital, Monza, and San Giuseppe Hospital, Milan) from January 1, 2011, to July 31, 2019. Methods: From a cohort of non-idiopathic pulmonary fibrosis fibrosing ILD patients with at least 2-year follow-up, we selected only those with progressive disease, defined as per the INBUILD trial, collecting their demographical, clinical, and functional data. Results: Out of the 245 fibrosing ILD patients, 75 (31%) were classified as PF-ILDs (median age 66 years, 60% males), most frequently idiopathic non-specific interstitial pneumonia (28%), followed by connective tissue disease-associated ILD (20%), chronic hypersensitivity pneumonitis, and sarcoidosis (17% each). Most patients (81%) were categorized as PF-ILDs because of forced vital capacity (FVC) decline ≥10%, while 19% experienced a marginal FVC decline (between 5 and 10%) associated with worsening respiratory symptoms or increasing extent of fibrotic changes on high-resolution computed tomography. Disease progression occurred after a median of 18 months from ILD diagnosis. The vast majority (93%) of PF-ILD patients received prednisolone, alone (40%) or associated with steroid-sparing agents (52%), and 35% of treated patients developed treatment-related adverse events. After ILD progression, the median survival was 3 (interquartile range (IQR) 2-5) years, with a 2- and 3-year mortality rate of 4 and 20%, respectively. Conclusions: In a real-life setting, approximately one-third of the fibrosing ILD patients showed a progressive course despite treatment. Studies aimed to better phenotype this subgroup of patients are needed.