The Efficacy of Interferon Beta in Delaying Conversion to Clinically Definite Multiple Sclerosis

More than half of patients with a clinically isolated syndrome (CIS) develop clinically definite multiple sclerosis (CDMS). Patients at high risk for CDMS often present with asymptomatic lesions characteristic of CDMS on magnetic resonance imaging scans, although an absence of asymptomatic lesions is not atypical. Phase 3 studies of interferon beta in patients with a CIS suggest that this treatment can delay conversion to CDMS and reduce the risk of new asymptomatic white matter lesions. We reviewed phase 3 studies (CHAMPS, BENEFIT, and ETOMS) and post hoc analyses assessing the efficacy of interferon beta in delaying CDMS in patients with a CIS. The evidence supports early initiation of treatment.