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Biased survival predictions when appraising health technologies in heterogeneous populations

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Gallacher, Daniel C., Kimani, Peter K. and Stallard, Nigel (2022) Biased survival predictions when appraising health technologies in heterogeneous populations. PharmacoEconomics - Open . pp. 109-120. doi:10.1007/s40273-021-01082-x ISSN 2509-4262.

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Official URL: https://doi.org/10.1007/s40273-021-01082-x

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Abstract

Introduction
Time-to-event data from clinical trials are routinely extrapolated using parametric models to estimate the cost effectiveness of novel therapies, but how this approach performs in the presence of heterogeneous populations remains unknown.

Methods
We performed a simulation study of seven scenarios with varying exponential distributions modelling treatment and prognostic effects across subgroup and complement populations, with follow-up typical of clinical trials used to appraise the cost effectiveness of therapies by agencies such as the UK National Institute for Health and Care Excellence (NICE). We compared established and emerging methods of estimating population life-years (LYs) using parametric models. We also proved analytically that an exponential model fitted to censored heterogeneous survival times sampled from two distinct exponential distributions will produce a biased estimate of the hazard rate and LYs.

Results
LYs are underestimated by the methods in the presence of heterogeneity, resulting in either under- or overestimation of the incremental benefit. In scenarios where the overestimation of benefit is likely, which is of interest to the healthcare provider, the method of taking the average LYs from all plausible models has the least bias. LY estimates from complete Kaplan–Meier curves have high variation, suggesting mature data may not be a reliable solution. We explore the effect of increasing trial sample size and accounting for detected treatment–subgroup interactions.

Conclusions
The bias associated with heterogeneous populations suggests that NICE may need to be more cautious when appraising therapies and to consider model averaging or the separate modelling of subgroups when heterogeneity is suspected or detected.

Item Type: Journal Article
Subjects: R Medicine > R Medicine (General)
Divisions: Faculty of Science, Engineering and Medicine > Medicine > Warwick Medical School
Library of Congress Subject Headings (LCSH): Medical technology -- Cost effectiveness, Technology assessment, Clinical trials -- Cost effectiveness -- Standards -- Great Britain, Technology assessment -- Evaluation
Journal or Publication Title: PharmacoEconomics - Open
Publisher: Springer
ISSN: 2509-4262
Official Date: January 2022
Dates:
DateEvent
January 2022Published
28 September 2021Available
19 August 2021Accepted
Page Range: pp. 109-120
DOI: 10.1007/s40273-021-01082-x
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Open Access (Creative Commons)
Date of first compliant deposit: 24 August 2021
Date of first compliant Open Access: 13 October 2021
RIOXX Funder/Project Grant:
Project/Grant IDRIOXX Funder NameFunder ID
14/25/05[NIHR] National Institute for Health Researchhttp://dx.doi.org/10.13039/501100000272
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