Therapeutic Response by Radiologic Pattern of Lung Injury in Myositis-Associated Interstitial Lung Disease: A Retrospective Cohort Study

Abstract Objective Myositis-associated interstitial lung disease (myositis-ILD) consists of two predominant radiologic patterns of lung injury—nonspecific interstitial pneumonia (NSIP) and organizing pneumonia (OP)—that oftentimes coexist. However, it remains unclear whether either is associated with clinical outcomes. We aimed to assess the therapeutic response in patients with NSIP-compared to those with OP-predominant myositis-ILD. Methods This retrospective, single-center cohort study recruited participants from the Northwestern University ILD Registry with a circulating myositis-associated antibody, ILD, and at least 6 months of follow-up while on immunomodulatory therapy during a 24-month observation period after diagnosis. Two thoracic radiologists determined the predominant radiologic pattern (NSIP or OP). The primary outcome was the absolute change in forced vital capacity (FVC) at 24 months post-diagnosis. Secondary outcomes included changes in the diffusing capacity of the lung for carbon monoxide (DLCO) and radiologic qualitative and quantitative measures of lung injury. Results Forty-one participants were included in analyses. 71% had an OP-predominant while 29% had an NSIP-predominant radiologic pattern of lung injury. Both exposure cohorts had improvement in mean absolute FVC (OP cohort = +0.18L [p=0.005], NSIP cohort = +0.24L [p=0.07]) over the 24-month observation period. The OP (p