Effects of relapsing-remitting multiple sclerosis treatment with interferon beta-1b results of a three-year follow-up study.

The aim of this prospective study was to evaluate therapeutic effects in a cohort of 32 patients with relapsing-remitting multiple sclerosis (RRMS) that were continuously treated with interferon beta-1b during a three-year period and to compare the results obtained with literature data available. Additionally, dropouts and side effects were assessed. The annual relapse rate at three years of treatment as the primary study end-point decreased by 60.5% compared with the relapse rate throughout the pretherapeutic course of disease (0.39 +/- 0.55 vs. 0.97 +/- 0.46; P<0.001) and by 71.3% compared with the relapse rate one year prior to treatment (0.39 +/- 0.55 vs. 1.34 +/- 0.65; P<0.001). The mean Extended Disability Status Scale (EDSS) increased significantly from 2.46 +/- 0.86 at baseline to 2.90 +/- 1.30 (P<0.01) at three years of treatment, whereas the mean progression index (EDSS/disease duration) decreased significantly from 0.76 +/- 0.50 prior to treatment to 0.43 +/- 0.24 (P<0.001), yielding a 56.6% improvement and proving the disease modifying effect of interferon beta-1b. Seventeen (53.12%) patients remained relapse-free during the course of therapy. Among patients that experienced disease relapse, the mean time to first exacerbation was 11.5 +/- 8.34 months. Our study results were consistent with similar studies performed worldwide, clearly indicating that Interferon beta-1b therapy decreased the disease activity and had a beneficial effect on the progression of RRMS, with low incidence and severity of serious side effects. This study has paved way for further long-term follow up studies at our institution.