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.