Does interferon really prevent disability?

A July 2012 article published in the Journal of Americal Medical Association concluded that treatment with interferon beta (Avonex, Betaserson and Rebif) was NOT associated  reduction in disability progression.   This result contradicts other interferon studies which demonstrated a benefit in preventing disability progression.   These earlier trials had led to FDA-approval of interferon treatments including Rebif and Avonex for lowering the risk of disability progression.

How can this study from University of British Columbia in Vancouver, Canada come up with a different result from the earlier studies?   This new study looked at database of patient information recorded over 4-5 years from British Columbia MS clinics.  A major difference is that this new Canadian study did not compare patients randomly assigned to interferon or placebo as opposed to the older studies.  They simply compared patients that were treated with interferon to those patients never treated.  The factors that influenced the decision for the doctor and patient to start interferon treatment or not treat are unknown.  The problem with the study is patients that were treated with interferon may have been at higher risk for disability progression compared to those patients that were not treated. 

No MRI information was included in the study.  MRI information such as high amount of disease activity or spinal cord inflammation may have influenced starting interferon in a group at higher risk for disability compared to a group of patients with little MRI activity and less risk of progression.  The treated patients had more relaspes in the 2 years prior to baseline and more disability at a younger age which increases the risk of disability in this group.

BOTTOM LINE:   Recommend staying the course with interferon treatment that has been proven to reduce MRI activity, new relapses and disability progression over at  2 years for relapsing patients.  Of note, the long-term benefit of inteferon treatment is difficult to scientifically to prove without a long-term placebo group  (which would be unethical to withhold treatment long term).