Idiopathic Pulmonary Fibrosis Disease Trajectory and Antifibrotic Therapy Outcomes: A Prospective Three-Year Cohort with Longitudinal Lung Function and Survival Analysis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with substantial heterogeneity in disease trajectory. Antifibrotic therapy with pirfenidone or nintedanib slows the rate of forced vital capacity (FVC) decline and modestly reduces mortality, but real-world treatment patterns and outcomes remain variable. We followed 185 patients with histologically or radiologically confirmed IPF prospectively at a tertiary interstitial lung disease clinic, stratifying by treatment status: early antifibrotic initiation within six months of diagnosis (n=98), late initiation more than six months after diagnosis (n=42), and never treated (n=45). Mean annual FVC decline was 95 mL/year in the early-treatment group, 185 mL/year in the late-treatment group, and 275 mL/year in untreated patients. Thirty-six-month survival was 75.6%, 60.9%, and 46.2% in the three groups respectively (log-rank p < 0.001). Independent predictors of rapid progression included baseline DLCO below 40% predicted, FVC below 60%, honeycombing extent above 25%, prior acute exacerbation, and GAP stage II or greater. Antifibrotic initiation reduced the odds of rapid progression by 66%. The findings reinforce the value of early antifibrotic initiation and structured surveillance for trajectory markers.