New natural history of interferon-β treated relapsing multiple sclerosis

Objective: To investigate the impact of interferon-beta (IFN beta) on disease progression in relapsing-remitting multiple sclerosis patients. Methods: A cohort of 1,504 relapsing-remitting multiple sclerosis (1,103 IFN beta-treated and 401 untreated) patients was followed for up to 7 years. Cox proportional hazards regression adjusted for propensity score inverse weighting was used to assess the differences between the two groups for three different clinical end points: secondary progression (SP) and irreversible Expanded Disability Status Scale (EDSS) scores 4 and 6. Times from first visit and from date of birth were used as survival time variables. Results-The IFN beta-treated group showed a highly significant reduction in the incidence of SP (hazard ratio [HR], 0.38, 95% confidence interval [CI], 0.24-0.58 for time from 1st visit; HR, 0.36, 95% CI, 0.23-0.56 for time from date of birth; p < 0.0001), EDSS score of 4 (HR, 0.70, 95% CI, 0.53-0.94 for time from first visit; HR, 0.69, 95% CI, 0.52-0.93 for time from date of birth; p < 0.02), and EDSS score of 6 (HR, 0.60, 95% CI, 0.38-0.95 for time from first visit; HR, 0.54, 95% CI, 0.34-0.86 for time from date of birth; p <= 0.03) when compared with untreated patients. SP and EDSS scores of 4 and 6 were reached with significant delays estimated by times from first visit (3.8, 1.7, and 2.2 years) and from date of birth (8.7, 4.6, and 11.7 years) in favor of treated patients. Sensitivity analysis confirmed findings. Interpretation: IFN-beta slows progression in relapsing-remitting multiple sclerosis patients.