Understanding Patterns of Adherence to Antifibrotic Treatment in Idiopathic Pulmonary Fibrosis: Insights from an Italian Prospective Cohort Study

Background: Pirfenidone and Nintedanib have significantly improved the prognosis of patients with idiopathic pulmonary fibrosis (IPF), reducing mortality risk and exacerbations. This study aimed to analyze antifibrotic treatment utilization and its association with clinical outcomes (i.e., acute exacerbation or death) during 2014–2021 in newly diagnosed IPF patients, using Healthcare Utilization Databases of the Marche Region, Italy. Methods: The first 12-month adherence to antifibrotic was estimated using the Proportion of Days Covered (PDC), defining adherence as PDC ≥ 75%. State Sequence Analysis over the initial 52 weeks of treatment was used to identify adherence patterns. The role of adherence patterns on acute exacerbations/death, adjusted by demographic, clinical features, and monthly adherence after the 52-week period (time-dependent variable), was assessed with Cox regression. Results: Among 667 new IPF cases, 296 received antifibrotic prescriptions, with 62.8% being adherent in the first year. Three antifibrotic utilization patterns emerged—high adherence (37.2%), medium adherence (42.5%), and low adherence (20.3%)—with median PDCs of 95.3%, 79.5%, and 18.6%, respectively. These patterns did not directly influence three-year mortality/exacerbation probability, but sustained adherence reduced risk over time. Conclusions: Good adherence was observed in in this population-based study, emphasizing the importance of continuous antifibrotics therapy over time to mitigate adverse outcomes.