Maguire, Melissa J., Hemming, Karla, Hutton, Jane L. and Marson, A. G.. (2008) Reporting and analysis of open-label extension studies of anti-epileptic drugs. Epilepsy Research, Vol.81 (No.1). pp. 24-29. ISSN 0920-1211

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Abstract

Purpose: Open-label extension studies, or follow-on randomised controlled trials (FORCTs) are widely believed to be prone to patient selection biases which may inflate effect estimates. This study investigates the reporting and analysis of efficacy outcomes in FORCTs and critically evaluates the associated underlying assumptions. We propose an alternative method of analysis, in line with that recommended in the analysis of RCTs, the intention to treat (ITT) approach, in which it is assumed that all patients who discontinue treatment are non-responders. Methods: A systematic review of FORCTs and randomised controlled trials (RCT) of topiramate, levetiracetam and gabapentin as adjuvant therapy in refractory adult epilepsy was conducted. Sample sizes and numbers of responders, along with reported outcomes were extracted. To evaluate the feasibility of the assumptions underlying the various methods of analysis, the most common causes of discontinuation were evaluated. For each FORCT, we compared the reported outcome to the proposed ITT analysis. Results: The 10 FORCT reports identified all excluded from the analysis patients who dropped out of the RCT. Adverse events or inefficacy were the main reasons for treatment discontinuation. Analysis based on the ITT method, led to smaller effect estimates than those reported. For example, a FORCT of levetiracetam reported a responder rate of 43%, which reduced to 28% under an ITT analysis, comparable to an ITT analysis outcome of 26% for the parent RCT. Conclusions: FORCTs can provide important information about tong-term efficacy and tolerability of newer therapies. However, current reporting methods are likely to be misleading as outcomes are reported for the subset of patients continuing with treatment at the end of the FORCT. Since the majority of patients who discontinue treatment do so for reasons associated with inefficacy, an analysis based on the ITT approach more closely reflects the outcomes of the patients. (C) 2008 Elsevier BX AR rights reserved.

Item Type:	Journal Article
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry R Medicine > RM Therapeutics. Pharmacology
Divisions:	Faculty of Science > Statistics
Library of Congress Subject Headings (LCSH):	Anticonvulsants -- Effectiveness, Clinical trials
Journal or Publication Title:	Epilepsy Research
Publisher:	Elsevier BV
ISSN:	0920-1211
Date:	September 2008
Volume:	Vol.81
Number:	No.1
Number of Pages:	6
Page Range:	pp. 24-29
Identification Number:	10.1016/j.eplepsyres.2008.04.007
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Medical Research Council (Great Britain) (MRC)
Grant number:	G0400642 (MRC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/29192

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