Objective: To examine MRI changes resulting from treatment of secondary pro
gressive MS (SPMS) with two doses of interferon-beta-1a (Rebif). Background
: Interferon-beta (IFN-P) reduces relapses and delays progression in relaps
ing-remitting MS, but there are conflicting results on its clinical benefit
in SPMS. Methods: In a double-blind, randomized, multicenter, placebo-cont
rolled study (SPECTRIMS), 618 patients received IFN-beta -1a 22 mug, 44 mug
, or placebo subcutaneously three times weekly for 3 years. T2 activity and
burden of disease (BOD) were measured in 617 patients by using semiannual
proton density/T2-weighted (PD/TS) MRI scans. A cohort of 283 patients also
had 11 monthly PD/T2 and T1-weighted gadolinium-enhanced (T1-Gd) scans at
study start. Results: Treatment reduced median numbers of active lesions pe
r patient per scan (semiannual T2 activity: 0.17, 0.20 and 0.67 for the hig
h dose, low dose, and placebo, p < 0.0001; monthly combined unique activity
[T1+T2]: 0.11, 0.22, and 1.00, p < 0.0001) and accumulation of BOD (percen
t change from baseline to month 36: -1.3, -0.5, and 10.0 for the high dose,
low dose, and placebo, respectively; p = 0.0001). MRI benefit was most evi
dent in the subgroup of patients who reported relapses in the 2 years befor
e the study. Neutralizing antibody development was associated with reductio
n in treatment effect: antibody-positive patients did not show significant
differences from placebo at either dose. Conclusions: Interferon-<beta>-1a
used in SPMS showed significant effects on all MRI measures, particularly i
n patients with relapses in the 2 years before the study.