Final analysis of the European multicenter trial on IFNβ-1b in secondary-progressive MS

Background: Based on a prospectively planned interim analysis, the European study of interferon beta -1b (IFN beta -1b) provided evidence that the treatment delays neurologic deterioration in patients with secondary progressive MS (SPMS). The authors analyzed all data collected until closure of the double-blind study to further scrutinize the consistency of the findings. Methods: The multicenter, double-blind, randomized, placebo-controlled trial treated patients for up to 36 months. The primary and all secondary endpoints of this study were evaluated using the data set at study termination, with a mean follow-up under double-blind conditions of 1054 +/- 199 and 1068 +/- 176 days for the placebo and IFN beta -1b group. Alternative and more demanding definitions of disease progression were explored. Confirmed progression was analyzed in subgroups according to baseline demographics and baseline indicators of disease activity. Results: Forty-eight of 358 placebo and 40 of 360 IFN beta -1b-allocated patients were lost to follow-up. Time to confirmed 1.0-point Expanded Disability Status Scale (EDSS) progression for patients receiving IFN beta -1b was delayed (p = 0.007). The proportion of patients with a confirmed 2.0-point EDSS progression was approximately 27% lower for the group treated with IFN beta -1b, both including and excluding EDSS data collected during relapses. The proportion of patients with either progression or relapses decreased by nearly 30% in patients treated with IFN beta -1b compared with placebo. Analysis of subgroups suggests that patients with higher prestudy disease activity (more than two relapses or EDSS progression by more than 1.0 point or both) seem to have a more pronounced treatment effect. Conclusion: Analysis of the data set at study termination including additional post hoc outcome measures is consistent with the original findings, thus supporting the conclusion that treatment with IFN beta -1b is effective in patients with SPMS fulfilling the inclusion criteria of this study.