Multiple Sclerosis Research Repository

“Association Between Use of Interferon Beta and Progression of Disability in Patients With Relapsing-Remitting Multiple Sclerosis” by Afsaneh Shirani, MD et al

-”Among patients with relapsing-remitting MS, administration of interferon beta was not associated with a reduction in progression of disability” 

-”Previous postmarketing studies have suggested a positive association between interferon beta and MS disability outcomes.^4–10,30 However, conducting adequately controlled longitudinal observational studies is challenging, and many such studies have faced methodological issues. One of the larger studies to date, from 2 Italian centers,¹⁰ was susceptible to immortal time bias^13,15 because of differing baselines for the treated and untreated cohorts. The use of a propensity score method in that study¹⁰ could not address immortal time bias. An independent reanalysis found no apparent beneficial association with interferon beta treatment once this bias was considered.¹³ Another methodological issue included the use of a control group comprising individuals too ill to start interferon beta treatment (owing to significant comorbidities).¹⁰ Both of these issues could bias the study to show a treatment effect when one might not exist.^12,13 Another relatively large Canadian study used patients as their own controls.⁵ This approach minimized some potential biases but may not have sufficiently acknowledged the variable and unpredictable individual progression profiles of MS patients.⁵ A sizable UK-based observational study was unable to demonstrate a beneficial association with the use of DMDs in relapsing-remitting MS after 2 years of treatment, finally concluding that further follow-up was needed”

-”we found that patients eligible for interferon beta treatment in the interferon beta era but who chose not to start treatment had a non–statistically significant more favorable overall outcome compared with those who started treatment in the same era. This may be explained by “indication bias,” whereby patients whose clinical status is not improving or is getting worse are prescribed drug therapy”

-”A 16-year follow-up of MS patients originally randomized to receive placebo or interferon beta treatment in a 2-year clinical trial was unable to show benefit in the treatment group in terms of progression to an EDSS score of 6 or secondary progressive MS”

-”no effect of interferon beta treatment on disability progression could be found in patients with clinically isolated syndrome (considered at high risk of developing MS)”