Cyclophosphamide for Systemic Sclerosis-related Interstitial Lung Disease: A Comparison of Scleroderma Lung Study I and II

Objective. To compare safety and efficacy outcomes between the cyclophosphamide (CYC) arms of Scleroderma Lung Study (SLS) I and II. Methods. Participants enrolled in the CYC arms of SLS I (n = 79) and II (n = 69) were included. SLS I and II randomized participants to oral CYC for 1 year and followed patients for an additional year off therapy (in SLS II, patients received placebo in Year 2). Eligibility criteria for SLS I and II were nearly identical. Outcomes included the forced vital capacity (FVC%)-predicted and DLCO%-predicted (measured every 3 mos) and quantitative radiographic extent of interstitial lung disease (measured at 1 and 2 yrs for SLS I and SLS II, respectively). Joint models were created to evaluate the treatment effect on the course of the FVC/DLCO over 2 years while controlling for baseline disease severity. Results. SLS I and II CYC participants had similar baseline characteristics. After adjusting for baseline disease severity, there was no difference in the course of the FVC%-predicted (p = 0.535) nor the DLCO%-predicted (p = 0.172) between the SLS I and II CYC arms. In both groups, treatment with CYC led to a significant improvement in the FVC%-predicted from 3 to 12 months, but no significant improvement beyond this point. Treatment with CYC had no effect on the DLCO for either group. Conclusion. Treatment with 1 year of oral CYC led to similar improvements in lung function in both SLS I and II, although the effects were not sustained following cessation of CYC. These results suggest that increasing the duration of ILD therapy may improve outcomes for patients with systemic sclerosis–ILD.