Aim: To investigate the long-term impact of interferon-beta (IFNbeta) therapy on disease severity in relapsing-remitting multiple sclerosis (RRMS) patients.
Patients and methods: We included 210 patients with RRMS and indication for immunomodulatory treatment followed up at least for nine years. We compared between treated and untreated groups: time since the beginning of the disease to reach EDSS 6.0 and time to conversion to secondary progressive multiple sclerosis. Log-rank test was used to compare outcomes between groups, p < 0.05 were considered significant.
Results: 160 patients were IFNbeta-treated, 50 untreated. The percentage of patients that converted to SPMS after 9 years of follow-up was 7.1% for treated vs. 21.7% for untreated (p = 0.022; RR = 0.32; 95% CI = 0.13-0.74). About 7.7% for IFNbeta-treated vs. 18.7% of untreated patients reached EDSS 6.0 after the period of follow-up (p = 0.032; RR = 0.4; 95% CI = 0.16-0.95). Mean time to reach EDSS 6.0 was 8.1 years for IFNbeta-treated vs. 5.8 years for untreated patients (p < 0.001).
Conclusion: Long term treatment with IFNbeta slows progression in MS measured by EDSS and time to conversion to secondary progressive multiple sclerosis.