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 microg, 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.