Long-term follow-up of clinical trials of multiple sclerosis therapies.

Results from registry studies can provide valuable information about the prevalence and clinical course of different forms of multiple sclerosis (MS). Such studies can also help identify medical practice patterns in a real-world setting and important risk factors that may affect long-term outcomes in patients with MS. To date, however, these observational studies have provided less information than well-planned, randomized, controlled trials on the long-term treatment effects of disease-modifying therapies (DMTs). Short-term clinical trial results have indicated that currently available DMTs are effective in reducing disease activity, manifested by relapse or MRI change, and may slow disease progression. Because MS is a chronic disease that evolves over a period of 30 to 40 years, determining the long-term effects of treatment is of critical importance to both patients and providers. This article discusses long-term studies of DMTs in patients with MS. Exploratory data provided thus far support the hypothesis that early optimal treatment aimed at reducing disease activity can improve longer-term outcomes by delaying disease progression.