Recent findings support greater efficacy of early vs. delayed interferon beta (IFNβ) treatment in patients with a first clinical event suggestive of multiple sclerosis (MS). We aimed to evaluate the effectiveness of early IFNβ treatment in definite relapsing-remitting MS (RRMS) and to assess the optimal time to initiate IFNβ treatment with regard to the greatest benefits on disability progression.
A cohort of 2,570 IFNβ-treated RRMS patients was prospectively followed for up to 7 years in 15 Italian MS Centers. A Cox proportional hazards regression model adjusted for propensity score (PS) quintiles was used to assess differences between groups of patients with early vs. delayed IFNβ treatment on risk of reaching a 1-point progression in the Expanded Disability Status Scale (EDSS) score, and the EDSS 4.0 and 6.0 milestones. A set of PS-adjusted Cox hazards regression models were calculated according to different times of treatment initiation (within 1 year up to within 5 years from disease onset). A sensitivity analysis was performed to assess the robustness of findings.
The lowest hazard ratios (HRs) for the three PS quintiles–adjusted models were obtained by a cutoff of treatment initiation within 1 year from disease onset. Early treatment significantly reduced the risk of reaching a 1-point progression in EDSS score (HR = 0.63; 95% CI = 0.48–0.85; p < 0.002), and the EDSS 4.0 milestone (HR = 0.56; 95% CI = 0.36–0.90; p = 0.015). Sensitivity analysis showed the bound of significance for unmeasured confounders.
Greater benefits on disability progression may be obtained by an early IFNβ treatment in RRMS. Ann Neurol 2009;66:513–520