Oral glucocorticoids added to ILD‐modifying therapy in systemic sclerosis‐associated interstitial lung disease: a target trial emulation study from the EUSTAR database.

OBJECTIVES: We aimed to estimate whether adding oral glucocorticoids to ILD-modifying therapy improves 12-month lung outcomes in systemic sclerosis-associated interstitial lung disease (SSc-ILD). METHODS: We emulated a target trial using the EUSTAR database. Eligible adults with confirmed SSc-ILD initiated an eligible ILD-modifying therapy at baseline (T0), either alone or with oral glucocorticoids added (prednisone-equivalent dose ≤20 mg/day). Follow-up ended at the visit closest to 12 months within a 9 to 15-month window. The primary outcome was the between-group difference in change in FVC (% predicted). Secondary outcomes were progressive lung fibrosis and isolated DLCO decline ≥15%. We used multiple imputation (m=80), stabilised inverse probability of treatment weighting, robust variance estimators and Rubin's rules. RESULTS: Of 443 patients, 185 (41.8%) received oral glucocorticoids with ILD-modifying therapy and 258 (58.2%) received ILD-modifying therapy alone. Adding oral glucocorticoids was not associated with improved 12-month FVC. The adjusted mean difference in FVC change was -2.10 percentage points (95% CI -4.68 to 0.47; p=0.11). There was no clear difference in progressive lung fibrosis (RR 1.40, 95% CI 0.83 to 2.35) or isolated DLCO decline ≥15% (RR 0.81, 95% CI 0.39 to 1.69). Findings were consistent in the truncated-weight sensitivity analysis. CONCLUSION: Adding oral glucocorticoids to ILD-modifying therapy was not associated with improved 12-month FVC in SSc-ILD. Secondary outcomes were sparse and should be interpreted cautiously.