Reporting and analysis of open-label extension studies of anti-epileptic drugs

M J Maguire; K Hemming; J L Hutton; A G Marson

doi:10.1016/j.eplepsyres.2008.04.007

Reporting and analysis of open-label extension studies of anti-epileptic drugs

M J Maguire, K Hemming, J L Hutton, A G Marson

Research output: Contribution to journal › Article › peer-review

10 Citations (Scopus)

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 long-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.

Original language	English
Pages (from-to)	24-9
Number of pages	6
Journal	Epilepsy Research
Volume	81
Issue number	1
Early online date	2 Jun 2008
DOIs	https://doi.org/10.1016/j.eplepsyres.2008.04.007
Publication status	Published - Sept 2008

Keywords

Amines
Anticonvulsants
Cyclohexanecarboxylic Acids
Databases, Factual
Drug Resistance
Epilepsy
Fructose
Humans
Patient Dropouts
Piracetam
Randomized Controlled Trials as Topic
Research Design
gamma-Aminobutyric Acid

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10.1016/j.eplepsyres.2008.04.007

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title = "Reporting and analysis of open-label extension studies of anti-epileptic drugs",

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 long-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.",

keywords = "Amines, Anticonvulsants, Cyclohexanecarboxylic Acids, Databases, Factual, Drug Resistance, Epilepsy, Fructose, Humans, Patient Dropouts, Piracetam, Randomized Controlled Trials as Topic, Research Design, gamma-Aminobutyric Acid",

author = "Maguire, {M J} and K Hemming and Hutton, {J L} and Marson, {A G}",

year = "2008",

month = sep,

doi = "10.1016/j.eplepsyres.2008.04.007",

language = "English",

volume = "81",

pages = "24--9",

journal = "Epilepsy Research",

issn = "0920-1211",

publisher = "Elsevier",

number = "1",

}

TY - JOUR

T1 - Reporting and analysis of open-label extension studies of anti-epileptic drugs

AU - Maguire, M J

AU - Hemming, K

AU - Hutton, J L

AU - Marson, A G

PY - 2008/9

Y1 - 2008/9

N2 - 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 long-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.

AB - 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 long-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.

KW - Amines

KW - Anticonvulsants

KW - Cyclohexanecarboxylic Acids

KW - Databases, Factual

KW - Drug Resistance

KW - Epilepsy

KW - Fructose

KW - Humans

KW - Patient Dropouts

KW - Piracetam

KW - Randomized Controlled Trials as Topic

KW - Research Design

KW - gamma-Aminobutyric Acid

U2 - 10.1016/j.eplepsyres.2008.04.007

DO - 10.1016/j.eplepsyres.2008.04.007

M3 - Article

C2 - 18514485

SN - 0920-1211

VL - 81

SP - 24

EP - 29

JO - Epilepsy Research

JF - Epilepsy Research

IS - 1

ER -

Reporting and analysis of open-label extension studies of anti-epileptic drugs

Abstract

Keywords

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