Several studies presented at the 2015 ECTRIMS Conference addressed the issue of how to assess treatment response after the first year, specifically whether the appearance of new MRI lesions or new relapses is reliable.
At least 7 studies have shown that newly diagnosed patients, started on interferon and assessed at 1 year, have very high probability, up to 90%, of doing well if they have no new MRI lesions. The most cited study was published in 2009 by Dr Luca Prosperini, involving 394 patients. Patients with no new T2 lesions on MRI at 1 year and no relapses had a 92% chance of having no added disability over the 4- to 5-year course of the study. One new T2 lesion reduced their probability to 50%, two to 30%, and 3 to 20%.
Dr Prosperini, however, noted that it may be difficult to be certain that a new MRI lesion may just be an artifact of the limitations or variability in image acquisition. The new consensus is that at least 2 T2 lesions or 1 or more gadolinium-enhancing lesions are required for confident prediction.
Other researchers believe that relapses and new lesions are both required to conclude that the patient is a “treatment failure.”
Lastly, it may be that the location of the lesions is more important than their number. Spinal cord and infratentorial (brainstem or cerebellum) were independent predictors of disability irrespective of the lesion count.
However one looks at the data, it is clear that patients started on a new medication must be monitored closely and that there be a low threshold to switch to more aggressive therapy.