Greater cumulative exposure to subcutaneous interferon beta-1a (IFN–beta-1a) may cause better outcomes in treatment of relapsing-remitting multiple sclerosis, according to Ludwig Kappos, Ph.D., of the departments of neurology, medicine, clinical research, biomedicine and biomedical engineering, University Hospital Basel, Switzerland, and his associates.

In the study, 290 patients received varying doses of subcutaneous IFN–beta-1a over a 15-year time period, and their MS progression was monitored. Patients in the maximum-dosage quartile had two fewer relapses on average: 5.8 versus 7.8 in the minimum-dosage quartile. About 57% of patients in the maximum-dosage group experienced five or fewer relapses, compared with only 40% in the minimum-dosage group.

Average progression on the Expanded Disability Status Scale was lower in the maximum-dosage group, which also had fewer patients experience progression than the minimum-dosage group. Conversion rate to secondary-progressive MS was also lower in the maximum-dosage group, with a hazard ratio of 0.31, compared with the minimum-dosage group.

In a related editorial, Dr. Fedor Heidenreich of the department of neurology and clinical neurophysiology, Diakoniekrankenhaus Henriettenstiftung in Hannover, Germany, said the study results “should prompt MS specialists to encourage patients to continue with IFN–beta-1a (or glatiramer acetate) treatment more resolutely instead of frequently switching their therapeutic regime.”

Find the full study and editorial online in the Sept. 16 Journal of Neurology, Neurosurgery, and Psychiatry.