An exploratory study on interferon beta dose effect in reducing size of enhancing lesions in multiple sclerosis.

Sixty-two patients with multiple sclerosis (MS) were imaged monthly over a six-month (ie, seven monthly magnetic resonance images [MRI]) natural history period (NHP). Thereafter, patients were randomized to receive 11 or 33 mug of subcutaneously injected interferon beta 1a (IFNp-1 a) with imaging monthly for nine months and at months 12, 18 and 24 of therapy phase (TP). In the present exploratory post hoc analysis, the authors evaluated IFNbeta-1a dose effect on reducing the size of contrast-enhancing lesions (CELs). MRIs performed at months 0, 3 and 6 of NHP and at months 3, 6, 9, 18 and 24 of TP were analysed. While a significant reduction in mean number of CELs was observed in both treatment groups of patients, the mean total volume and size of CELs was reduced only in patients undergoing therapy with 33 mug of IFNbeta-1a. The latter suggests a significant dose effect exerted by IFNbeta-1a in the evolution of CELs' dimensions during therapy.