Regular magnetic resonance imaging (MRI) evaluations show that only about half of patients with multiple sclerosis achieve and sustain a response to treatment with interferon beta over three years, according to a study posted online today that will appear in the January 2009 print issue of Archives of Neurology.
Before they develop symptoms of a relapse, patients with multiple sclerosis (MS) develop contrast-enhancing brain lesions that are visible on MRI, according to background information in the article. Worsening of the disease is presumed to follow these relapses. "Many clinical studies have demonstrated the ability of interferon beta to reduce contrast-enhancing lesions," the authors write. "However, little is known regarding the heterogeneity of the MRI response profiles between patients or within an individual patient over time."
Annie W. Chiu, B.S., and colleagues at the National Institute of Neurological Disorders and Stroke, Bethesda, Md., assessed 15 patients with MS who underwent monthly MRIs and clinical examinations during a six-month pretreatment phase and a 36-month treatment phase. During treatment, patients receive injections of 250 micrograms of interferon beta under the skin every other day.
Eight patients (53.3 percent) achieved a 60 percent reduction in the number of lesions at each six-month period and were therefore classified as responders. Of the seven non-responders, three (20 percent) initially experienced a reduction in the total number of lesions but then did not experience further reductions, two (13.3 percent) never reached the 60 percent level of reduction and two (13.3 percent) failed to respond during the first six months but reached and maintained an optimal reduction in lesions of 60 percent or more thereafter. Three patients in the responder group and all seven patients in the non-responder group experienced at least one clinical exacerbation during the treatment phase.
"To our knowledge, our descriptive study provides for the first time a detailed long-term analysis of MRI patterns of patients undergoing long-term interferon beta-1b therapy," the authors conclude. "The results show that on close monthly MRI inspection, approximately half of the patients fail therapy from an MRI perspective."
"Also, we show that an additional small proportion of patients may not be necessarily recognized as MRI non-responders during the first semester [six months] of therapy, and frequent radiological monitoring is advised during the first year of therapy. Multiple MRIs, beyond the first six months of therapy, also disclose a small proportion of patients with a delayed but eventually sustained response to interferon beta and provide compelling information regarding the clinical outcome of patients during the course of a longer trial."