Long-term disability outcomes in relapsing-remitting multiple sclerosis: a 10-year follow-up study

The aim of this study is to assess the impact of interferon (IFN) beta treatment on the development of worsening disability in relapsing-remitting (RR) multiple sclerosis (MS) patients in the single-center observation cohort.

This is a prospective study of 236 IFN-beta-treated and 183 untreated RRMS patients recruited consecutively at the Clinic of Neurology in Belgrade (Serbia). Out of this original cohort, 10-year follow-up data were available for 233 IFN-beta-treated and 131 untreated subjects. The median time since recruitment was 9.7 years.

IFN-beta treatment significantly delayed (p < 0.001) the time to reach each of the clinical outcomes (secondary progression-SP, EDSS scores 4 and 6) since recruitment. Time from the first visit to SP was reached after 9.7 years for IFN-beta-treated vs. 7.8 years for untreated patients. The delay for the development of EDSS score ≥ 4 from the first visit was 1.6 years (8.7 years for IFN-beta-treated vs. 7.1 years for untreated patients). Time from the first visit to EDSS score of 6 was reached after 9.8 years for IFN-beta-treated vs. 8.8 years for untreated patients. The IFN-beta-treated group showed significant reduction (p < 0.001) in the risk of conversion to SP when compared with untreated patients (HR = 0.22). There was also a significant difference in reaching EDSS scores 4 and 6 (p < 0.001), in favor of the IFN-beta-treated group (HR = 0.40 and HR = 0.27, respectively).

Comparison of outcomes in our IFN-beta-treated vs. untreated RRMS patients suggests that this treatment may delay development of long-term disability in MS.