Progressive pulmonary fibrosis and its impact on survival in systemic sclerosis-related interstitial lung disease

Objective: To describe the frequency of progressive pulmonary fibrosis (PPF) in an incident cohort of systemic sclerosis (SSc)-related interstitial lung disease (ILD) and its impact on survival. Methods: Incident ILD was defined as the new development of characteristic fibrotic changes on chest HRCT scan. PPF was defined as per the 2022 American Thoracic Society. Determinants of PPF were identified using generalised estimating equations. Impact on survival was analysed using accelerated failure time regression modelling. Results: Of our incident SSc-ILD cases, 38.8% (n = 180) experienced PPF within a 12-month period after ILD diagnosis. Determinants of PPF included older age (OR 1.02, 95%CI 1.00-1.03, P = 0.011), dcSSc (OR 1.54, 95% CI 1.06-2.25, P = 0.024) and SSc-specific antibodies (anticentomere antibody OR 0.51, 95%CI 0.29-0.91, P = 0.021 and anti-Scl-70 antibody OR 1.46, 95%CI 1.01-2.09, P = 0.043). Raised CRP was numerically associated with PPF but did not reach statistical significance (OR 1.29, 95%CI 0.99-1.68, P = 0.064) nor did GORD or dysphagia (OR 1.18, 95%CI 0.57-2.42, P = 0.658 and OR 1.17, 95%CI 0.57-2.40, P = 0.664, respectively). The presence of PPF significantly impacted survival in SSc-ILD (hazard ratio 2.66, 95%CI 1.59-4.41, P < 0.001). Conclusions: PPF occurred in a third of our incident SSc-ILD cohort; however, its occurrence was significantly associated with mortality indicating an at-risk group who may be suitable for earlier introduction of immunosuppressive and/or antifibrotic therapy.