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Title: Assessing methods for dealing with treatment switching in clinical trials: A follow-up simulation study
Authors: Latimer, Nicholas R.
Abrams, Keith R.
Lambert, Paul C.
Morden, James P.
Crowther, Michael J.
First Published: 25-Apr-2016
Publisher: SAGE Publications
Citation: Statistical Methods in Medical Research, 2016, in press
Abstract: When patients randomised to the control group of a randomised controlled trial are allowed to switch onto the experimental treatment, intention-to-treat analyses of the treatment effect are confounded because the separation of randomised groups is lost. Previous research has investigated statistical methods that aim to estimate the treatment effect that would have been observed had this treatment switching not occurred and has demonstrated their performance in a limited set of scenarios. Here, we investigate these methods in a new range of realistic scenarios, allowing conclusions to be made based upon a broader evidence base. We simulated randomised controlled trials incorporating prognosis-related treatment switching and investigated the impact of sample size, reduced switching proportions, disease severity, and alternative data-generating models on the performance of adjustment methods, assessed through a comparison of bias, mean squared error, and coverage, related to the estimation of true restricted mean survival in the absence of switching in the control group. Rank preserving structural failure time models, inverse probability of censoring weights, and two-stage methods consistently produced less bias than the intention-to-treat analysis. The switching proportion was confirmed to be a key determinant of bias: sample size and censoring proportion were relatively less important. It is critical to determine the size of the treatment effect in terms of an acceleration factor (rather than a hazard ratio) to provide information on the likely bias associated with rank-preserving structural failure time model adjustments. In general, inverse probability of censoring weight methods are more volatile than other adjustment methods.
DOI Link: 10.1177/0962280216642264
eISSN: 1477-0334
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © the author(s) 2016. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 3.0 License ( which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (
Appears in Collections:Published Articles, Dept. of Health Sciences

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