Effect of early interferon treatment on conversion to definite multiple sclerosis: a randomised study

Background Interferon beta reduces activity in multiple sclerosis as measured clinically and by magnetic resonance imaging (MRI). We assessed the effect of interferon beta-1a on the occurrence of relapses in patients after first presentation with neurological events, who are at high risk of conversion to clinically definite multiple sclerosis. Methods Eligible patients had had a first episode of neurological dysfunction suggesting multiple sclerosis within the previous 3 months and had strongly suggestive brain MRI findings. Patients were randomly assigned interferon beta-1a 22 μg or placebo subcutaneously once weekly for 2 years. Neurological and clinical assessments were done every 6 months and brain MRI every 12 months. Analyses excluded one patient assigned placebo who received no study injections. Findings 241 (78%) of 308 randomised patients received study treatment for 2 years; 278 (90%) remained in the study until termination. 57 (85%) of 67 who stopped therapy did so after conversion to clinically definite multiple sclerosis. Fewer patients developed clinically definite multiple sclerosis in the interferon group than in the placebo group (52/154 [34%] vs 69/154 [45%]; p=0·047). The time at which 30% of patients had converted to clinically definite multiple sclerosis was 569 days in the interferon group and 252 in the placebo group (p=0·034). The annual relapse rates were 0·33 and 0·43 (p=0·045). The number of new T2-weighted MRI lesions and the increase in lesion burden were significantly lower with active treatment. Interpretation Interferon beta-1a treatment at an early stage of multiple sclerosis had significant positive effects on clinical and MRI outcomes.