By Harvey McConnell
There is still a lack of solid evidence that recombinant interferons are effective after a year of treatment for patients with relapsing multiple sclerosis.
Interferons have been approved by many national regulatory agencies for almost a decade after clinical trials established that interferon beta preparations reduced disease activity. However, doubts remain as to whether they can really prevent progression of the disease, and the effect is sustained over time.
As interferons are now widely used in clinical practice, Dr Graziella Filippini and colleagues at the Cochrane Multiple Sclerosis Review Group, National Neurological Institute Milan, Italy, and Dr C Ebers, Department of Clinical Neurology, University of Oxford, England, considered the evidence. They reviewed all published, randomised, placebo-controlled trials of recombinant interferons undertaken in patients with relapsing remitting MS between 1993 and 2002.
In seven trials with 1,215 randomised patients: data from 667 patients (55%) were available for analysis at 1 year and from 919 patients (76%) at 2-year follow-up.
Interferon seemed to reduce the number of patients who had exacerbations by about 25% during the first year of treatment but, at two years the clinicians found results "were not robust and were difficult to interpret because of the many dropouts." In addition, side-effects were common, and acute toxic effects adversely affected patients' quality of life.
Dr Filippini, in a comment on the study, said that while she and her colleagues conclude there is evidence for a modest effect of interferon in the first year of treatment, any effects after that are not clear. "Future trials should be better designed, all patients followed with minimal or no dropouts, and their reporting improved in order to allow better use of available data."
Dr Ebers said the data "highlight both the limitations of available data and the inadequate documentation of long term effects. This problem is not unique to MS but is found in many chronic diseases."
One solution could involve long term licensing of treatments in these conditions directly tied to mandatory follow-up of the original study patients . "This may be the only timely and efficient way to accurately determine the true effectiveness of therapies in these common disorders," Dr Ebers added.
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