Heterogeneity in Response to Interferon Beta in Patients With Multiple Sclerosis A 3-Year Monthly Imaging Study

Objectives: To investigate the heterogeneity in magnetic resonance image (MRI) patterns of response to interferon beta across patients with multiple sclerosis or within an individual patient over time. Design, Setting, and Patients: Fifteen patients with relapsing-remitting multiple sclerosis underwent monthly MRIs and clinical examinations (6-month pretherapy phase and 36-month therapy phase) and bimonthly neutralizing antibody tests. On each MRI, the total number of contrast-enhancing lesions was noted. Therapy MRI responders were defined as those with a reduction of 60% or more in the total number of contrast-enhancing lesions during each semester of therapy. Intervention: Subcutaneous administration of interferon beta-1b, 250 mu g, every other day for 3 years. Main Outcome Measure: Reduction in the number of contrast-enhancing lesions. Results: Eight patients (53.3%) were MRI responders and 7 (46.7%) were nonresponders. Of those 7, 3 (20.0%) had only an initial optimal reduction of the total number of contrast-enhancing lesions, 2 (13.3%) never reached an optimal response, and 2 ( 13.3%) had a delayed optimal response. No clear association between neutralizing antibody profile and MRI response was evident. Conclusions: Multiple MRI evaluations disclose that approximately only half of the patients treated with interferon beta achieve and maintain a full response to the drug over time, although an additional small number of individuals may still restore an optimal response to the drug after an initial failure.