PURPOSE OF REVIEW: In this review, the authors describe therapeutic strategies for a disease group called progressive fibrosing interstitial lung disease (PF-ILD) and highlight the importance of the definition of progression, prognosis, and treatment response. RECENT FINDINGS: Although it is a relatively new concept, the term PF-ILD has been increasingly applied in clinical research and practice. Three domains commonly used to detect the disease progression include clinical symptoms, rate of forced vital capacity (FVC) decline and the extent of fibrosis on imaging. Although details of the pathogenesis of PF-ILD are still unclear, it has become apparent that genetic predisposition and an abnormal tissue microenvironment and host response are involved in the nature of the disease. Antifibrotic agents recently showed their efficacy on the treatment of PF-ILD. Both nintedanib and pirfenidone can slow the disease progression, as defined by a decline of FVC from baseline, of PF-ILD whenever compared with placebo, similar to the results in idiopathic pulmonary fibrosis (IPF) trials. This effect seems consistent irrespective of the underlying ILD diagnosis. SUMMARY: Recent evidence supports the use of antifibrotic therapy in the management of the phenotype progressive non-IPF ILD. Ongoing studies exploring genetic and other molecular biomarkers could identify at-risk individuals or predict treatment response and prognosis (endotypes). This would support the concept of 'treatable traits' in the field of ILD.
