April 2, 2003
By Jill Stein
African-Americans with multiple sclerosis (MS) may have a decreased response to treatment with interferon beta-1a (Rebif), researchers announced here April 1st at the 55th Annual Meeting of the American Academy of Neurology.
Lead researcher Dr. Bruce C. Cree and associates at the University of California at San Francisco's Multiple Sclerosis Center evaluated disease activity in 36 African-Americans and 616 Caucasian-Americans with MS who were enrolled in the EVIDENCE (Evidence of Interferon Dose-Response: European North American Comparative Efficacy) trial.
The EVIDENCE trial compared the efficacy of 48 weeks of treatment with interferon beta-1a 44 mcg given 3 times a week with interferon beta-1a 30 mcg given once a week (Avonex).
While African-Americans may be less susceptible to MS than Caucasian-Americans, the disease course in African-American patients may be more severe, Dr. Cree pointed out, and they are at higher risk of developing secondary progressive MS and disability.
For the present sub-analysis, his group hypothesized that the severity of disease in African-Americans may be associated with reduced efficacy of treatment with interferon beta-1a.
Results showed that African-American patients were less likely to be exacerbation-free and experienced a greater number of exacerbations. African-American patients had a greater number of combined unique lesions at 24 weeks and a greater number of T2 lesions at 24 weeks than Caucasians.
These results, Dr. Cree said, were not likely to be due to African-American patients having more disease activity at baseline because they had similar baseline magnetic resonance imaging-combined unique lesions and attack rates in the 2 years prior to the study.
Overall, African-American patients had 0.55 times lesser odds of being relapse-free than Caucasians at 48 weeks adjusting for the baseline relapse rate in the 2 years prior to the study and the treatment effect (P=0.10). African-Americans had 0.31 more relapses than Caucasian-Americans at 48 weeks, adjusting for baseline relapse count and treatment effect (P=0.21).
African-Americans had 0.96 more new T2 lesions at 48 weeks than Caucasians, adjusting for baseline T2 lesions and treatment effect (P=0.04). African-Americans had 0.51 times lesser odds of having no new T2 lesions at 48 weeks than Caucasians, adjusting for baseline T2 lesions and treatment (P=0.09).
Similar results were found for the 24- week outcome measures.
Despite the very small number of African-Americans included in this study, the results showed that they responded less well to interferon beta-1a than Caucasians on all outcome measures, Dr. Cree said. These results reached statistical significance only for the T2 lesion count at 48 weeks.
The authors emphasized that while the findings point up a possible decreased treatment response in African-American patients, the sample size was small.
They added that further studies on the interaction between ethnicity and response to interferon beta-1a treatment are warranted and efforts should be made to enroll persons of diverse ethnicity in MS treatment trials.
The trial was supported by Serono, Inc.
[Study title: Multiple Sclerosis Disease Activity in Patients of Different
Ethnic Origin: Data from the Evidence Trial. P01.120]
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