Long-Term Follow up of Treatment with Interferon Beta 1-b in a Cohort of 87 Patients with Multiple Sclerosis: A 23-Year Observational Study in a Single Center

Background: IFN-beta-1b is the first disease-modifying therapy approved for MS. Data from short and 10 year follow up of patients enrolled in clinical trials with IFN-beta demonstrated a safe profile and 30% reduction in relapses with early treatment that may improve long term outcome.

Objectives: To describe outcomes of a cohort of patients treated with interferon (IFN) beta-1b 23 years ago.

Methods: The study setting was an integrated health care system in southeastern Michigan. Electronic and chart medical records of patients who started treatment with IFN beta-1b in 1993-1994 were reviewed. Sociodemographic, relapses, EDSS and treatment data were collected. Descriptive statistics were used. 

Results: Of the 87 patient, 71% were female, 86% were white, the mean age at diagnosis was 35 years (s.d.=9), and the mean age at the start of IFN beta 1-b treatment was 40.4years (s.d.=8.2). In the 79 patients with known duration of IFN beta-1b use, 29% used for < 1 year, 35% used for 1 to < 5 years and 18% used for 15+ years. The mean EDSS at the start of treatment was 3.9 (s.d.=1.8), while the mean EDSS at last visit was 4.4 (s.d.=2). 1 patient died and 8 were lost for follow up. Of the 68 patients who stopped treatment, side effects were reported by 57%, while lack of efficacy was reported by 16%. The side effects reason was more common in the patients with shorter duration, < 5 years of use, while the lack of efficacy was more common in the patients who stopped treatment after an extended duration of use.

Conclusions: We present the longest follow up of a clinical practice cohort of patients started on IFN beta-1b 23 years ago. While short term effect of interferon beta treatment is well known from clinical trials, understanding long term effect and benefit of treatment is important for this lifelong disease that affects young adults.