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

Background Interferon beta reduces activity in multiple sclerosis as measur ed clinically and by magnetic resonance imaging (MRI). We assessed the effe ct of interferon beta-1a on the occurrence of relapses in patients after fi rst presentation with neurological events, who are at high risk of conversi on to clinically definite multiple sclerosis. Methods Eligible patients had had a first episode of neurological dysfuncti on suggesting multiple sclerosis within the previous 3 months and had stron gly suggestive brain MRI findings. Patients were randomly assigned interfer on beta-1a 22 mug or placebo subcutaneously once weekly for 2 years. Neurol ogical and clinical assessments were done every 6 months and brain MRI ever y 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 clinica lly definite multiple sclerosis was 569 days in the interferon group and 25 2 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 s clerosis had significant positive effects on clinical and MRI outcomes.