Long-term follow-up of multiple sclerosis studies and outcomes from early treatment of clinically isolated syndrome in the BENEFIT 11 study.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) with a diverse disease course involving inflammation and degeneration of neurons and axons. Multiple sclerosis results from a complex interaction of genetic and environmental factors and clinically several disease subtypes with marked variation in symptoms can be discerned. Disease-modifying therapies (DMTs) impact disease activity and outcome. Long-term follow-up studies of DMTs in MS have generally shown that the short-term effects in clinical trials are maintained for up to 21 years, e.g. in the case of interferon beta-1b. However, attainment can be a problem in these studies. On the one hand, so-called real-world studies can augment clinical trials by providing data on the long-term effectiveness and safety of DMTs but lack, on the other hand, randomization and may, in addition, also yield biased findings as a result of compliance issues. Long-term data from clinical trials in clinically isolated syndrome (CIS) patients have been limited but in the case of interferon beta-1b this aspect has been addressed over 11 years in the BENEFIT 11 trial. The results suggest that early treatment results in persistent long-term benefits including conversion to clinically definite MS (CDMS) as well as time to and risk of a first relapse. Here we primarily review the findings of the BENEFIT 11 trial in the context of long-term studies.