Initiation of antifibrotic treatment in fibrosing interstitial lung disease: is the clock ticking till proven progression?

Several interstitial lung diseases (ILDs) with different aetiologies and pathogenic mechanisms may exhibit a progressive behaviour, similar to idiopathic pulmonary fibrosis, with comparable functional decline and early mortality. Progressive pulmonary fibrosis (PPF) is not a diagnosis but rather reflects a clinical phenotype. Identifying progression is challenging as variability exists, both between different ILDs as well as in the context of the same entity. The American Thoracic Society/European Respiratory Society guidelines provide a useful framework for recognising the progressive behaviour of individual ILDs. Nevertheless, sometimes the "one-size-fits-all" approach to PPF may not lead to the best management decisions for individual patients. Real-life clinical practice presents multiple hurdles for practising clinicians and it is of utmost importance to target early those individuals that will benefit from antifibrotic treatment. This review aims to highlight several clinical points and suggest that, in certain cases, the strict rule of initiating antifibrotic treatment only upon disease progression may warrant some flexibility, particularly in the context of everyday clinical practice. Emphasis is placed on critically examining the criteria used to define progression across different ILDs, commenting on clinical issues such as disease severity at baseline, prevention of acute exacerbations, the definition of "standard treatment", the need for early access to appropriate treatment, prediction of progression, personalised medicine and an aetiologic approach. Engaging technology and artificial intelligence will play a role in the future. Until then, the best possible management decisions will rely on the judgment of treating clinicians, guided by existing evidence and patient needs.