Characteristics and disease course of untreated patients with interstitial lung disease associated with systemic sclerosis in a real-life two-centre cohort

Background Interstitial lung disease (ILD) is the leading cause of death in systemic sclerosis (SSc). According to expert statements, not all SSc-ILD patients require pharmacological therapy.Objectives To describe disease characteristics and disease course in untreated SSc-ILD patients in two well characterised SSc-ILD cohorts.Methods Patients were classified as treated if they had received a potential ILD-modifying drug. ILD progression in untreated patients was defined as (1) decline in forced vital capacity (FVC) from baseline of ≥10% or (2) decline in FVC of 5%–9% associated with a decline in diffusing capacity for carbon monoxide (DLCO)≥15% over 12±3 months or (3) start of any ILD-modifying treatment or (4) increase in the ILD extent during follow-up. Multivariable logistic regression was performed to identify factors associated with non-prescription of ILD-modifying treatment at baseline. Prognostic factors for progression in untreated patients were tested by multivariate Cox regression.Results Of 386 SSc-ILD included patients, 287 (74%) were untreated at baseline. Anticentromere antibodies (OR: 6.75 (2.16–21.14), p=0.001), limited extent of ILD (OR: 2.39 (1.19–4.82), p=0.015), longer disease duration (OR: 1.04 (1.00–1.08), p=0.038) and a higher DLCO (OR: 1.02 (1.01–1.04), p=0.005) were independently associated with no ILD-modifying treatment at baseline. Among 234 untreated patients, the 3 year cumulative incidence of progression was 39.9% (32.9–46.2). Diffuse cutaneous SSc and extensive lung fibrosis independently predicted ILD progression in untreated patients.Conclusion As about 40% of untreated patients show ILD progression after 3 years and effective and safe therapies for SSc-ILD are available, our results support a change in clinical practice in selecting patients for treatment.