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Pin L, Villar SS, Dehbi HM. Implementing and assessing Bayesian response-adaptive randomisation for backfilling in dose-finding trials. Contemp Clin Trials 2024:107567. [PMID: 38729298 DOI: 10.1016/j.cct.2024.107567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/29/2024] [Accepted: 05/04/2024] [Indexed: 05/12/2024]
Abstract
Traditional approaches in dose-finding trials, such as the continual reassessment method, focus on identifying the maximum tolerated dose. In contemporary early-phase dose-finding trials, especially in oncology with targeted agents or immunotherapy, a more relevant aim is to identify the lowest dose level that maximises efficacy whilst remaining tolerable. Backfilling, defined as the practice of assigning patients to dose levels lower than the current highest tolerated dose, has been proposed to gather additional pharmacokinetic, pharmacodynamic and biomarker data to recommend the most appropriate dose to carry forward for subsequent studies. The first formal framework [5] for backfilling proposed randomising backfill patients with equal probability among those doses below the dose level where the study is currently at. Here, we propose to use Bayesian response-adaptive randomisation to backfill patients. This patient-oriented approach to backfilling aims to allocate more patients to dose levels in the backfill set with higher expected efficacy based on emerging data. The backfill set constitutes of the doses below the dose the dose-finding algorithm is at. At study completion, collective patient data inform the dose-response curve, suggesting an optimal dose level balancing toxicity and efficacy. Our simulation study across diverse clinical trial settings demonstrates that a backfilling strategy using Bayesian response-adaptive randomisation can result in a patient-oriented patient assignment procedure which simultaneously enhances the likelihood of correctly identifying the most appropriate dose level. This contribution offers a methodological framework and practical implementation for patient-oriented backfilling, encompassing design and analysis considerations in early-phase trials.
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Affiliation(s)
- Lukas Pin
- MRC Biostatistics Unit at University of Cambridge, Cambridge, UK
| | - Sofía S Villar
- MRC Biostatistics Unit at University of Cambridge, Cambridge, UK
| | - Hakim-Moulay Dehbi
- Comprehensive Clinical Trials Unit at University College London, London, UK.
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2
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Heath B, Evans S, Robertson DS, Robotham JV, Villar SS, Presanis AM. Evaluating pooled testing for asymptomatic screening of healthcare workers in hospitals. BMC Infect Dis 2023; 23:900. [PMID: 38129789 PMCID: PMC10740241 DOI: 10.1186/s12879-023-08881-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 12/07/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND There is evidence that during the COVID pandemic, a number of patient and HCW infections were nosocomial. Various measures were put in place to try to reduce these infections including developing asymptomatic PCR (polymerase chain reaction) testing schemes for healthcare workers. Regularly testing all healthcare workers requires many tests while reducing this number by only testing some healthcare workers can result in undetected cases. An efficient way to test as many individuals as possible with a limited testing capacity is to consider pooling multiple samples to be analysed with a single test (known as pooled testing). METHODS Two different pooled testing schemes for the asymptomatic testing are evaluated using an individual-based model representing the transmission of SARS-CoV-2 in a 'typical' English hospital. We adapt the modelling to reflect two scenarios: a) a retrospective look at earlier SARS-CoV-2 variants under lockdown or social restrictions, and b) transitioning back to 'normal life' without lockdown and with the omicron variant. The two pooled testing schemes analysed differ in the population that is eligible for testing. In the 'ward' testing scheme only healthcare workers who work on a single ward are eligible and in the 'full' testing scheme all healthcare workers are eligible including those that move across wards. Both pooled schemes are compared against the baseline scheme which tests only symptomatic healthcare workers. RESULTS Including a pooled asymptomatic testing scheme is found to have a modest (albeit statistically significant) effect, reducing the total number of nosocomial healthcare worker infections by about 2[Formula: see text] in both the lockdown and non-lockdown setting. However, this reduction must be balanced with the increase in cost and healthcare worker isolations. Both ward and full testing reduce HCW infections similarly but the cost for ward testing is much less. We also consider the use of lateral flow devices (LFDs) for follow-up testing. Considering LFDs reduces cost and time but LFDs have a different error profile to PCR tests. CONCLUSIONS Whether a PCR-only or PCR and LFD ward testing scheme is chosen depends on the metrics of most interest to policy makers, the virus prevalence and whether there is a lockdown.
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Affiliation(s)
- Bethany Heath
- MRC Biostatistics Unit, Univeristy of Cambridge, Robinson Way, Cambridge, CB2 0SR, Cambridgeshire, United Kingdom.
| | - Stephanie Evans
- HCAI, Fungal, AMR, AMU and Sepsis Division, UK Health Security Agency, London, United Kingdom
- Statistics, Modelling and Economics Division, UK Health Security Agency, London, United Kingdom
| | - David S Robertson
- MRC Biostatistics Unit, Univeristy of Cambridge, Robinson Way, Cambridge, CB2 0SR, Cambridgeshire, United Kingdom
| | - Julie V Robotham
- HCAI, Fungal, AMR, AMU and Sepsis Division, UK Health Security Agency, London, United Kingdom
- Statistics, Modelling and Economics Division, UK Health Security Agency, London, United Kingdom
- NIHR Health Protection Research Unit in Modelling and Health Economics at Imperial College London in partnership with the UK Health Security Agency and London School of Hygiene and Tropical Medicine, London, United Kingdom
- NIHR Health Protection Research Unit in Healthcare Associated Infections and Antimicrobial Resistance at University of Oxford in partnership with the UK Health Security Agency, Oxford, United Kingdom
| | - Sofía S Villar
- MRC Biostatistics Unit, Univeristy of Cambridge, Robinson Way, Cambridge, CB2 0SR, Cambridgeshire, United Kingdom
| | - Anne M Presanis
- MRC Biostatistics Unit, Univeristy of Cambridge, Robinson Way, Cambridge, CB2 0SR, Cambridgeshire, United Kingdom
- NIHR Health Protection Research Unit in Behavioural Science and Evaluation at University of Bristol in partnership with the UK Health Security Agency and MRC Biostatistics Unit, University of Cambridge, Bristol, United Kingdom
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Law M, Couturier DL, Choodari-Oskooei B, Crout P, Gamble C, Jacko P, Pallmann P, Pilling M, Robertson DS, Robling M, Sydes MR, Villar SS, Wason J, Wheeler G, Williamson SF, Yap C, Jaki T. Correction: Medicines and Healthcare products Regulatory Agency's "Consultation on proposals for legislative changes for clinical trials": a response from the Trials Methodology Research Partnership Adaptive Designs Working Group, with a focus on data sharing. Trials 2023; 24:744. [PMID: 37990330 PMCID: PMC10664262 DOI: 10.1186/s13063-023-07763-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2023] Open
Affiliation(s)
- Martin Law
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK.
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK.
| | - Dominique-Laurent Couturier
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
| | | | - Phillip Crout
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - Carrol Gamble
- Liverpool Clinical Trials Centre, University of Liverpool, Liverpool, UK
| | - Peter Jacko
- Lancaster University Management School, Lancaster University, Lancaster, UK
- Berry Consultants, Abingdon, UK
| | | | - Mark Pilling
- Department of Public Health and Primary Care, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - David S Robertson
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | | | - Matthew R Sydes
- University College London, London, UK
- British Heart Foundation Data Science Centre, Health Data Research UK, London, UK
| | - Sofía S Villar
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - James Wason
- Bio- Statistics Research Group, Population Health Sciences Institute, Newcastle Uni-Versity, Newcastle Upon Tyne, UK
| | - Graham Wheeler
- Imperial Clinical Trials Unit, Imperial College London, London, W12 7RH, UK
| | - S Faye Williamson
- Bio- Statistics Research Group, Population Health Sciences Institute, Newcastle Uni-Versity, Newcastle Upon Tyne, UK
| | - Christina Yap
- Clinical Trials and Statistics Unit, The Institute of Cancer Research, London, UK
| | - Thomas Jaki
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Faculty for Informatics and Data Science, University of Regensburg, Regensburg, Germany
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4
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Law M, Couturier DL, Choodari-Oskooei B, Crout P, Gamble C, Jacko P, Pallmann P, Pilling M, Robertson DS, Robling M, Sydes MR, Villar SS, Wason J, Wheeler G, Williamson SF, Yap C, Jaki T. Medicines and Healthcare products Regulatory Agency's "Consultation on proposals for legislative changes for clinical trials": a response from the Trials Methodology Research Partnership Adaptive Designs Working Group, with a focus on data sharing. Trials 2023; 24:640. [PMID: 37798805 PMCID: PMC10552399 DOI: 10.1186/s13063-023-07576-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 08/04/2023] [Indexed: 10/07/2023] Open
Abstract
In the UK, the Medicines and Healthcare products Regulatory Agency consulted on proposals "to improve and strengthen the UK clinical trials legislation to help us make the UK the best place to research and develop safe and innovative medicines". The purpose of the consultation was to help finalise the proposals and contribute to the drafting of secondary legislation. We discussed these proposals as members of the Trials Methodology Research Partnership Adaptive Designs Working Group, which is jointly funded by the Medical Research Council and the National Institute for Health and Care Research. Two topics arose frequently in the discussion: the emphasis on legislation, and the absence of questions on data sharing. It is our opinion that the proposals rely heavily on legislation to change practice. However, clinical trials are heterogeneous, and as a result some trials will struggle to comply with all of the proposed legislation. Furthermore, adaptive design clinical trials are even more heterogeneous than their non-adaptive counterparts, and face more challenges. Consequently, it is possible that increased legislation could have a greater negative impact on adaptive designs than non-adaptive designs. Overall, we are sceptical that the introduction of legislation will achieve the desired outcomes, with some exceptions. Meanwhile the topic of data sharing - making anonymised individual-level clinical trial data available to other investigators for further use - is entirely absent from the proposals and the consultation in general. However, as an aspect of the wider concept of open science and reproducible research, data sharing is an increasingly important aspect of clinical trials. The benefits of data sharing include faster innovation, improved surveillance of drug safety and effectiveness and decreasing participant exposure to unnecessary risk. There are already a number of UK-focused documents that discuss and encourage data sharing, for example, the Concordat on Open Research Data and the Medical Research Council's Data Sharing Policy. We strongly suggest that data sharing should be the norm rather than the exception, and hope that the forthcoming proposals on clinical trials invite discussion on this important topic.
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Affiliation(s)
- Martin Law
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK.
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK.
| | - Dominique-Laurent Couturier
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
| | | | - Phillip Crout
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - Carrol Gamble
- Liverpool Clinical Trials Centre, University of Liverpool, Liverpool, UK
| | - Peter Jacko
- Lancaster University Management School, Lancaster University, Lancaster, UK
- Berry Consultants, Abingdon, UK
| | | | - Mark Pilling
- Department of Public Health and Primary Care, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - David S Robertson
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | | | - Matthew R Sydes
- University College London, London, UK
- British Heart Foundation Data Science Centre, Health Data Research UK, London, UK
| | - Sofía S Villar
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - James Wason
- Biostatistics Research Group, Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Graham Wheeler
- Imperial Clinical Trials Unit, Imperial College London, London, W12 7RH, UK
| | - S Faye Williamson
- Biostatistics Research Group, Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Christina Yap
- Clinical Trials and Statistics Unit, The Institute of Cancer Research, London, UK
| | - Thomas Jaki
- Medical Research Council Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Faculty for Informatics and Data Science, University of Regensburg, Regensburg, Germany
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5
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Abstract
Response-Adaptive Randomization (RAR) is part of a wider class of data-dependent sampling algorithms, for which clinical trials are typically used as a motivating application. In that context, patient allocation to treatments is determined by randomization probabilities that change based on the accrued response data in order to achieve experimental goals. RAR has received abundant theoretical attention from the biostatistical literature since the 1930's and has been the subject of numerous debates. In the last decade, it has received renewed consideration from the applied and methodological communities, driven by well-known practical examples and its widespread use in machine learning. Papers on the subject present different views on its usefulness, and these are not easy to reconcile. This work aims to address this gap by providing a unified, broad and fresh review of methodological and practical issues to consider when debating the use of RAR in clinical trials.
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Affiliation(s)
- David S. Robertson
- MRC Biostatistics Unit, University of Cambridge, Forvie Site, Robinson Way, Cambridge CB2 0SR, United Kingdom
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6
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Barnett HY, Villar SS, Geys H, Jaki T. A novel statistical test for treatment differences in clinical trials using a response-adaptive forward-looking Gittins Index Rule. Biometrics 2023; 79:86-97. [PMID: 34669968 PMCID: PMC7614356 DOI: 10.1111/biom.13581] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/30/2021] [Indexed: 11/28/2022]
Abstract
The most common objective for response-adaptive clinical trials is to seek to ensure that patients within a trial have a high chance of receiving the best treatment available by altering the chance of allocation on the basis of accumulating data. Approaches that yield good patient benefit properties suffer from low power from a frequentist perspective when testing for a treatment difference at the end of the study due to the high imbalance in treatment allocations. In this work we develop an alternative pairwise test for treatment difference on the basis of allocation probabilities of the covariate-adjusted response-adaptive randomization with forward-looking Gittins Index (CARA-FLGI) Rule for binary responses. The performance of the novel test is evaluated in simulations for two-armed studies and then its applications to multiarmed studies are illustrated. The proposed test has markedly improved power over the traditional Fisher exact test when this class of nonmyopic response adaptation is used. We also find that the test's power is close to the power of a Fisher exact test under equal randomization.
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Affiliation(s)
| | - Sofía S Villar
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
| | | | - Thomas Jaki
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
- Medical and Pharmaceutical Statistics Research Unit, Lancaster University, Lancaster, UK
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7
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Mavrogonatou L, Sun Y, Robertson DS, Villar SS. A comparison of allocation strategies for optimising clinical trial designs under variance heterogeneity. Comput Stat Data Anal 2022. [DOI: 10.1016/j.csda.2022.107559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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8
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Warren A, McKie MA, Villar SS, Camporota L, Vuylsteke A. Effect of Hypoxemia on Outcome in Respiratory Failure Supported With Extracorporeal Membrane Oxygenation: A Cardinality Matched Cohort Study. ASAIO J 2022; 68:e235-e242. [PMID: 36301178 PMCID: PMC7613891 DOI: 10.1097/mat.0000000000001835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Venovenous extracorporeal membrane oxygenation (ECMO) is recommended in adult patients with refractory acute respiratory failure (ARF), but there is limited evidence for its use in patients with less severe hypoxemia. Prior research has suggested a lower PaO 2 /FiO 2 at cannulation is associated with higher short-term mortality, but it is unclear whether this is due to less severe illness or a potential benefit of earlier ECMO support. In this exploratory cardinality-matched observational cohort study, we matched 668 patients who received venovenous ECMO as part of a national severe respiratory failure service into cohorts of "less severe" and "very severe" hypoxemia based on the median PaO 2 /FiO 2 at ECMO institution of 68 mmHg. Before matching, ICU mortality was 19% in the 'less severe' hypoxemia group and 28% in the "very severe" hypoxemia group (RR for mortality = 0.69, 95% CI 0.54-0.88). After matching on key prognostic variables including underlying diagnosis, this difference remained statistically present but smaller: (23% vs. 30%, RR = 0.76, 95% CI 0.59-0.99). This may suggest the observed survival benefit of venovenous ECMO is not solely due to reduced disease severity. Further research is warranted to examine the potential role of ECMO in ARF patients with less severe hypoxemia.
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Affiliation(s)
- Alex Warren
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Cambridge, UK
- Critical Care Unit, Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
| | - Mikel A. McKie
- Biostatistics Unit, Cambridge Institute of Public Health, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Papworth Trials Unit Collaboration, Cambridge, UK
| | - Sofía S. Villar
- Biostatistics Unit, Cambridge Institute of Public Health, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Papworth Trials Unit Collaboration, Cambridge, UK
| | - Luigi Camporota
- Division of Asthma, Allergy and Lung Biology, King’s College London, London, UK
- Department of Critical Care, Guy’s & St. Thomas’s Hospitals, London, UK
| | - Alain Vuylsteke
- Critical Care Unit, Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
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9
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Wason JMS, Dimairo M, Biggs K, Bowden S, Brown J, Flight L, Hall J, Jaki T, Lowe R, Pallmann P, Pilling MA, Snowdon C, Sydes MR, Villar SS, Weir CJ, Wilson N, Yap C, Hancock H, Maier R. Practical guidance for planning resources required to support publicly-funded adaptive clinical trials. BMC Med 2022; 20:254. [PMID: 35945610 PMCID: PMC9364623 DOI: 10.1186/s12916-022-02445-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 06/20/2022] [Indexed: 11/15/2022] Open
Abstract
Adaptive designs are a class of methods for improving efficiency and patient benefit of clinical trials. Although their use has increased in recent years, research suggests they are not used in many situations where they have potential to bring benefit. One barrier to their more widespread use is a lack of understanding about how the choice to use an adaptive design, rather than a traditional design, affects resources (staff and non-staff) required to set-up, conduct and report a trial. The Costing Adaptive Trials project investigated this issue using quantitative and qualitative research amongst UK Clinical Trials Units. Here, we present guidance that is informed by our research, on considering the appropriate resourcing of adaptive trials. We outline a five-step process to estimate the resources required and provide an accompanying costing tool. The process involves understanding the tasks required to undertake a trial, and how the adaptive design affects them. We identify barriers in the publicly funded landscape and provide recommendations to trial funders that would address them. Although our guidance and recommendations are most relevant to UK non-commercial trials, many aspects are relevant more widely.
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Affiliation(s)
- James M S Wason
- Biostatistics Research Group, Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK.
| | - Munyaradzi Dimairo
- School of Health and Related Research, Clinical Trials Research Unit, University of Sheffield, Sheffield, UK
| | - Katie Biggs
- School of Health and Related Research, Clinical Trials Research Unit, University of Sheffield, Sheffield, UK
| | - Sarah Bowden
- Cancer Research UK Clinical Trials Unit (CRCTU), University of Birmingham, Birmingham, UK
| | - Julia Brown
- Cancer Research UK CTU, University of Leeds, Leeds, UK
| | - Laura Flight
- School of Health and Related Research, Health Economics and Decision Science, University of Sheffield, Sheffield, UK
| | - Jamie Hall
- School of Health and Related Research, Clinical Trials Research Unit, University of Sheffield, Sheffield, UK
| | - Thomas Jaki
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
- Department of Mathematics and Statistics, Lancaster University, Lancaster, UK
| | - Rachel Lowe
- Centre for Trials Research, Cardiff University, Cardiff, UK
| | | | - Mark A Pilling
- Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
| | - Claire Snowdon
- The Institute of Cancer Research Clinical Trials & Statistics Unit, London, UK
| | | | - Sofía S Villar
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
| | - Christopher J Weir
- Edinburgh Clinical Trials Unit, Usher Institute, University of Edinburgh, Edinburgh, UK
| | - Nina Wilson
- Biostatistics Research Group, Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Christina Yap
- The Institute of Cancer Research Clinical Trials & Statistics Unit, London, UK
| | - Helen Hancock
- Newcastle Clinical Trials Unit, Newcastle University, Newcastle upon Tyne, UK
| | - Rebecca Maier
- Newcastle Clinical Trials Unit, Newcastle University, Newcastle upon Tyne, UK
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10
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Grayling MJ, Wason JMS, Villar SS. Response adaptive intervention allocation in stepped-wedge cluster randomized trials. Stat Med 2022; 41:1081-1099. [PMID: 35064595 PMCID: PMC7612601 DOI: 10.1002/sim.9317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 11/30/2021] [Accepted: 12/22/2021] [Indexed: 11/09/2022]
Abstract
BACKGROUND Stepped-wedge cluster randomized trial (SW-CRT) designs are often used when there is a desire to provide an intervention to all enrolled clusters, because of a belief that it will be effective. However, given there should be equipoise at trial commencement, there has been discussion around whether a pre-trial decision to provide the intervention to all clusters is appropriate. In pharmaceutical drug development, a solution to a similar desire to provide more patients with an effective treatment is to use a response adaptive (RA) design. METHODS We introduce a way in which RA design could be incorporated in an SW-CRT, permitting modification of the intervention allocation during the trial. The proposed framework explicitly permits a balance to be sought between power and patient benefit considerations. A simulation study evaluates the methodology. RESULTS In one scenario, for one particular RA design, the proportion of cluster-periods spent in the intervention condition was observed to increase from 32.2% to 67.9% as the intervention effect was increased. A cost of this was a 6.2% power drop compared to a design that maximized power by fixing the proportion of time in the intervention condition at 45.0%, regardless of the intervention effect. CONCLUSIONS An RA approach may be most applicable to settings for which the intervention has substantial individual or societal benefit considerations, potentially in combination with notable safety concerns. In such a setting, the proposed methodology may routinely provide the desired adaptability of the roll-out speed, with only a small cost to the study's power.
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Affiliation(s)
- Michael J Grayling
- Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - James M S Wason
- Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Sofía S Villar
- MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
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11
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Wilson N, Biggs K, Bowden S, Brown J, Dimairo M, Flight L, Hall J, Hockaday A, Jaki T, Lowe R, Murphy C, Pallmann P, Pilling MA, Snowdon C, Sydes MR, Villar SS, Weir CJ, Welburn J, Yap C, Maier R, Hancock H, Wason JMS. Costs and staffing resource requirements for adaptive clinical trials: quantitative and qualitative results from the Costing Adaptive Trials project. BMC Med 2021; 19:251. [PMID: 34696781 PMCID: PMC8545558 DOI: 10.1186/s12916-021-02124-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 09/13/2021] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Adaptive designs offer great promise in improving the efficiency and patient-benefit of clinical trials. An important barrier to further increased use is a lack of understanding about which additional resources are required to conduct a high-quality adaptive clinical trial, compared to a traditional fixed design. The Costing Adaptive Trials (CAT) project investigated which additional resources may be required to support adaptive trials. METHODS We conducted a mock costing exercise amongst seven Clinical Trials Units (CTUs) in the UK. Five scenarios were developed, derived from funded clinical trials, where a non-adaptive version and an adaptive version were described. Each scenario represented a different type of adaptive design. CTU staff were asked to provide the costs and staff time they estimated would be needed to support the trial, categorised into specified areas (e.g. statistics, data management, trial management). This was calculated separately for the non-adaptive and adaptive version of the trial, allowing paired comparisons. Interviews with 10 CTU staff who had completed the costing exercise were conducted by qualitative researchers to explore reasons for similarities and differences. RESULTS Estimated resources associated with conducting an adaptive trial were always (moderately) higher than for the non-adaptive equivalent. The median increase was between 2 and 4% for all scenarios, except for sample size re-estimation which was 26.5% (as the adaptive design could lead to a lengthened study period). The highest increase was for statistical staff, with lower increases for data management and trial management staff. The percentage increase in resources varied across different CTUs. The interviews identified possible explanations for differences, including (1) experience in adaptive trials, (2) the complexity of the non-adaptive and adaptive design, and (3) the extent of non-trial specific core infrastructure funding the CTU had. CONCLUSIONS This work sheds light on additional resources required to adequately support a high-quality adaptive trial. The percentage increase in costs for supporting an adaptive trial was generally modest and should not be a barrier to adaptive designs being cost-effective to use in practice. Informed by the results of this research, guidance for investigators and funders will be developed on appropriately resourcing adaptive trials.
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Affiliation(s)
- Nina Wilson
- Population Health Sciences Institute, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
| | - Katie Biggs
- School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
| | - Sarah Bowden
- Cancer Research UK Clinical Trials Unit (CRCTU), University of Birmingham, Birmingham, UK
| | - Julia Brown
- Leeds Institute of Clinical Trials Research, University of Leeds, Leeds, UK
| | - Munyaradzi Dimairo
- School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
| | - Laura Flight
- School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
| | - Jamie Hall
- School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
| | - Anna Hockaday
- Leeds Institute of Clinical Trials Research, University of Leeds, Leeds, UK
| | - Thomas Jaki
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
- Department of Mathematics and Statistics, Lancaster University, Lancaster, UK
| | - Rachel Lowe
- Centre for Trials Research, Cardiff University, Cardiff, UK
| | - Caroline Murphy
- King's College Trials Unit, King's College London, London, UK
| | | | - Mark A Pilling
- Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
| | - Claire Snowdon
- The Institute of Cancer Research Clinical Trials & Statistics Unit, London, UK
| | | | - Sofía S Villar
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
| | - Christopher J Weir
- Edinburgh Clinical Trials Unit, Usher Institute, University of Edinburgh, Edinburgh, UK
| | - Jessica Welburn
- School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
| | - Christina Yap
- The Institute of Cancer Research Clinical Trials & Statistics Unit, London, UK
| | - Rebecca Maier
- Population Health Sciences Institute, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
- Newcastle Clinical Trials Unit, Newcastle University, Newcastle upon Tyne, UK
| | - Helen Hancock
- Population Health Sciences Institute, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
- Newcastle Clinical Trials Unit, Newcastle University, Newcastle upon Tyne, UK
| | - James M S Wason
- Population Health Sciences Institute, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK.
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12
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Wilkins MR, Mckie MA, Law M, Roussakis AA, Harbaum L, Church C, Coghlan JG, Condliffe R, Howard LS, Kiely DG, Lordan J, Rothman A, Suntharalingam J, Toshner M, Wort SJ, Villar SS. Positioning imatinib for pulmonary arterial hypertension: A phase I/II design comprising dose finding and single-arm efficacy. Pulm Circ 2021; 11:20458940211052823. [PMID: 34868551 PMCID: PMC8642118 DOI: 10.1177/20458940211052823] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/19/2021] [Indexed: 12/21/2022] Open
Abstract
Pulmonary arterial hypertension is an unmet clinical need. Imatinib, a tyrosine kinase inhibitor, 200 to 400 mg daily reduces pulmonary artery pressure and increases functional capacity in this patient group, but is generally poorly tolerated at the higher dose. We have designed an open-label, single-arm clinical study to investigate whether there is a tolerated dose of imatinib that can be better targeted to patients who will benefit. The study consists of two parts. Part 1 seeks to identify the best tolerated dose of Imatinib in the range from 100 and up to 400 mg using a Bayesian Continuous Reassessment Method. Part 2 will measure efficacy after 24 weeks treatment with the best tolerated dose using a Simon's two-stage design. The primary efficacy endpoint is a binary variable. For patients with a baseline pulmonary vascular resistance (PVR) >1000 dynes · s · cm-5, success is defined by an absolute reduction in PVR of ≥300 dynes · s · cm-5 at 24 weeks. For patients with a baseline PVR ≤1000 dynes · s · cm-5, success is a 30% reduction in PVR at 24 weeks. PVR will also be evaluated as a continuous variable by genotype as an exploratory analysis. Evaluating the response to that dose by genotype may inform a prospective biomarker-driven study.
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Affiliation(s)
- Martin R. Wilkins
- National Heart and Lung Institute, Faculty of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Mikel A. Mckie
- MRC Biostatistics Unit, School of Clinical Medicine, Cambridge Institute of Public Health, Cambridge, UK
| | - Martin Law
- MRC Biostatistics Unit, School of Clinical Medicine, Cambridge Institute of Public Health, Cambridge, UK
| | | | - Lars Harbaum
- Golden Jubilee National Hospital, University of Glasgow, Scotland, UK
| | - Colin Church
- Royal Free Hospital, Royal Free London NHS Foundation Trust, London, UK
| | - J Gerry Coghlan
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
| | - Robin Condliffe
- Sheffield Pulmonary Vascular Disease Unit, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Luke S Howard
- National Pulmonary Hypertension Service, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, UK
| | - David G Kiely
- Newcastle Freeman Hospital, Freeman Road, High Heaton, Newcastle Upon Tyne, UK
| | - Jim Lordan
- Royal United Hospital, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK
| | - Alexander Rothman
- Heart Lung Research Institute, University of Cambridge, Cambridge, UK
| | | | - Mark Toshner
- Royal Brompton Hospital, Guy’s and St Thomas’s Trust, London, UK
| | - Stephen J Wort
- Royal Brompton Hospital, Guy’s and St Thomas’s Trust, London, UK
| | - Sofía S. Villar
- MRC Biostatistics Unit, School of Clinical Medicine, Cambridge Institute of Public Health, Cambridge, UK
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13
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Affiliation(s)
- Sofía S Villar
- Medical Research Council Biostatistics Unit, University of Cambridge, Institute of Public Health Forvie Site, Cambridge, United Kingdom
| | - David S Robertson
- Medical Research Council Biostatistics Unit, University of Cambridge, Institute of Public Health Forvie Site, Cambridge, United Kingdom
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14
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McKinney A, Weisblatt EJ, Hotson KL, Bilal Ahmed Z, Dias C, BenShalom D, Foster J, Murphy S, Villar SS, Belmonte MK. Overcoming hurdles to intervention studies with autistic children with profound communication difficulties and their families. Autism 2021; 25:1627-1639. [PMID: 33827289 PMCID: PMC8323331 DOI: 10.1177/1362361321998916] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Autistic children and adults who are non-verbal/minimally verbal or have an
intellectual disability have often been excluded from Autism Spectrum Disorder
research. Historical, practical and theoretical reasons for this exclusion
continue to deter some researchers from work with this underserved population.
We discuss why these reasons are neither convincing nor ethical, and provide
strategies for dealing with practical issues. As part of a randomised controlled
trial of an intervention for children with profound autism, we reflected as a
multi-disciplinary team on what we had learnt from these children, their
families and each other. We provide 10 strategies to overcome what appeared
initially to be barriers to collecting data with this population. These hurdles
and our solutions are organised by theme: interacting physically with children,
how to play and test, navigating difficult behaviours, selecting suitable
outcome measures, relating with parents, managing siblings, involving
stakeholders, timing interactions, the clinician’s role in managing
expectations, and recruitment. The aim of this article is to provide researchers
with the tools to feel motivated to conduct research with children with profound
autism and their families, a difficult but worthwhile endeavour. Many of these
lessons also apply to conducting research with non-autistic children with
intellectual disabilities.
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Affiliation(s)
- Ailbhe McKinney
- Nottingham Trent University, UK.,The University of Edinburgh, UK
| | - Emma Jl Weisblatt
- University of Cambridge, UK.,Cambridgeshire and Peterborough NHS Foundation Trust, UK
| | | | | | - Claudia Dias
- Cambridgeshire and Peterborough NHS Foundation Trust, UK
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15
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Warren A, Chiu YD, Villar SS, Fowles JA, Symes N, Barker J, Camporota L, Harvey C, Ledot S, Scott I, Vuylsteke A. Outcomes of the NHS England National Extracorporeal Membrane Oxygenation Service for adults with respiratory failure: a multicentre observational cohort study. Br J Anaesth 2020; 125:259-266. [PMID: 32736826 DOI: 10.1016/j.bja.2020.05.065] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/26/2020] [Accepted: 05/27/2020] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Extracorporeal membrane oxygenation (ECMO) is increasingly used to support adults with severe respiratory failure refractory to conventional measures. In 2011, NHS England commissioned a national service to provide ECMO to adults with refractory acute respiratory failure. Our aims were to characterise the patients admitted to the service, report their outcomes, and highlight characteristics potentially associated with survival. METHODS An observational cohort study was conducted of all patients treated by the NHS England commissioned ECMO service between December 1, 2011 and December 31, 2017. Analysis was conducted according to a prespecified protocol (NCT: 03979222). Data are presented as median [inter-quartile range, IQR]. RESULTS A total of 1205 patients were supported with ECMO during the study period; the majority (n=1150; 95%) had veno-venous ECMO alone. The survival rate at ECMO ICU discharge was 74% (n=887). Survivors had a lower median age (43 yr [32-52]), compared with non-survivors (49 y [39-60]). Increased severity of hypoxaemia at time of decision-to-cannulate was associated with a lower probability of survival: survivors had a median Sao2 of 90% (84-93%; median Pao2/Fio2, 9.4 kPa [7.7-12.6]), compared with non-survivors (Sao2 88% [80-92%]; Pao2/Fio2 ratio: 8.5 kPa [7.1-11.5]). Patients requiring ECMO because of asthma were more likely to survive (95% survival rate (95% CI, 91-99%), compared with a survival of 71% (95% CI, 69-74%) in patients with respiratory failure attributable to other diagnoses. CONCLUSION A national ECMO service can achieve good short-term outcomes for patients with undifferentiated respiratory failure refractory to conventional management. CLINICAL TRIAL REGISTRATION NCT03979222.
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Affiliation(s)
- Alex Warren
- Division of Anaesthesia, Department of Medicine, School of Clinical Medicine, University of Cambridge, Cambridge, UK; Critical Care Unit, Royal Papworth Hospital, Cambridge, UK
| | - Yi-Da Chiu
- MRC Biostatistics Unit, Cambridge Institute of Public Health, School of Clinical Medicine, University of Cambridge, Cambridge, UK; Clinical Trials Unit, Royal Papworth Hospital, Cambridge, UK
| | - Sofía S Villar
- MRC Biostatistics Unit, Cambridge Institute of Public Health, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - Jo-Anne Fowles
- Critical Care Unit, Royal Papworth Hospital, Cambridge, UK
| | - Nicola Symes
- Highly Specialised Services, NHS England, London, UK
| | - Julian Barker
- Cardiothoracic Critical Care Unit, Wythenshawe Hospital, Manchester, UK
| | - Luigi Camporota
- Department of Critical Care, Guy's & St Thomas' Hospitals, London, UK; Division of Asthma, Allergy and Lung Biology, King's College London, London, UK
| | - Chris Harvey
- University Hospitals of Leicester, Leicester, UK
| | - Stephane Ledot
- Adult Intensive Care Unit, Royal Brompton & Harefield Hospitals, London, UK
| | - Ian Scott
- Intensive Care Unit, Aberdeen Royal Infirmary, Aberdeen, UK
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16
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Affiliation(s)
- J H Mackay
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
| | - J W Brand
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
| | - Y D Chiu
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
| | - S S Villar
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
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17
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McKinney A, Hotson KL, Rybicki A, Weisblatt EJL, Días C, Foster J, Villar SS, Murphy S, Belmonte MK. Point OutWords: protocol for a feasibility randomised controlled trial of a motor skills intervention to promote communicative development in non-verbal children with autism. Trials 2020; 21:109. [PMID: 31973713 PMCID: PMC6979327 DOI: 10.1186/s13063-019-3931-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 11/23/2019] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Point OutWords is a caregiver-delivered, iPad-assisted intervention for non-verbal or minimally verbal children with autism. It aims to develop prerequisite skills for communication such as manual and oral motor skills, sequencing, and symbolic representation. This feasibility trial aims to determine the viability of evaluating the clinical efficacy of Point OutWords. METHODOLOGY We aim to recruit 46 non-verbal or minimally verbal children with autism and their families, approximately 23 per arm. Children in the intervention group will use Point OutWords for half an hour, five times a week, for 8 weeks. Children in the control group will have equal caregiver-led contact time with the iPad using a selection of control apps (e.g. sensory apps, drawing apps). Communication, motor, and daily living skills are assessed at baseline and post-intervention. Parents will keep diaries during the intervention period and will take part in focus groups when the intervention is completed. DISCUSSION Point OutWords was developed in collaboration with children with autism and their caregivers, to provide an intervention for a subgroup of autism that has been historically underserved. As autism is a heterogeneous condition, it is unlikely that one style of intervention will address all aspects of its symptomatology; the motor skills approach of Point OutWords can complement other therapies that address core autistic symptoms of social cognition and communication more directly. The current feasibility trial can inform the selection of outcome measures and design for future full-scale randomised controlled trials of Point OutWords and of other early interventions in autism. TRIAL REGISTRATION ISRCTN, ISRCTN12808402. Prospectively registered on 12 March 2019.
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Affiliation(s)
- Ailbhe McKinney
- Division of Psychology, Nottingham Trent University, Nottingham, UK
| | | | - Alicia Rybicki
- School of Psychology, University of Birmingham, Birmingham, UK
| | - Emma J. L. Weisblatt
- Department of Psychology, University of Cambridge, Cambridge, UK
- Peterborough Integrated Neurodevelopmental Service, Cambridgeshire and Peterborough NHS Foundation Trust, Peterborough, UK
| | - Claudia Días
- Peterborough Integrated Neurodevelopmental Service, Cambridgeshire and Peterborough NHS Foundation Trust, Peterborough, UK
| | - Juliet Foster
- Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Sofía S. Villar
- MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - Suzanne Murphy
- Institute for Health Research, University of Bedfordshire, Bedford, UK
| | - Matthew K. Belmonte
- Division of Psychology, Nottingham Trent University, Nottingham, UK
- The Com DEALL Trust, Bangalore, India
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18
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Naruka V, Mckie MA, Khushiwal R, Clayton J, Aresu G, Peryt A, Villar SS, MacKay J, Coonar AS. Acute kidney injury after thoracic surgery: a proposal for a multicentre evaluation (MERITS). Interact Cardiovasc Thorac Surg 2019; 29:861-866. [PMID: 31393555 DOI: 10.1093/icvts/ivz184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 06/19/2019] [Accepted: 06/26/2019] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES Because the mortality rate is very low in thoracic surgery, its use as a quality discriminator is limited. Acute kidney injury (AKI) is a candidate measure because it is associated with increased rates of morbidity and mortality and is partly preventable. The incidence of AKI after thoracic surgery is not well documented. We conducted an audit to determine the incidence and outcomes of AKI. This audit became a pilot project, and the results indicate the feasibility of a larger study. METHODS Retrospective data on renal function post-thoracic surgery were collected at a tertiary cardiothoracic unit over 12 months. Renal impairment was classified according to the Kidney Disease Improving Global Outcomes criteria. RESULTS Of 568 patients (mean = 59 ± SD 18; 38% women), AKI was diagnosed in 86 (15.1%) within 72 h post-thoracic surgery based on the Kidney Disease Improving Global Outcomes staging system (stage 1, n = 55; stage 2, n = 25; stage 3, n = 6). Significant differences were found in postoperative length of stay (3 vs 5 days; P < 0.001) of patients with and without AKI. There was a significant difference between the age groups of patients with and without AKI (P < 0.05) in the open surgical group but not in the group having video-assisted thoracoscopic surgery (VATS). There was no significant difference in the mortality rates between patients with and without AKI. CONCLUSIONS The incidence of AKI after thoracic surgery was 15.1%. AKI was associated with longer hospital stays and was more likely in ≥60-year-old patients after open surgery than after VATS. Reducing AKI could improve patient outcomes. We propose that AKI may be a useful quality measure in thoracic surgery. We are developing a multicentre audit based on this approach.
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Affiliation(s)
- Vinci Naruka
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
| | - Mikel A Mckie
- Department of Cambridge Institute of Public Health, Medical Research Council Biostatistics Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK
| | - Rasoel Khushiwal
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
| | - James Clayton
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
| | - Giuseppe Aresu
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
| | - Adam Peryt
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
| | - Sofía S Villar
- Department of Cambridge Institute of Public Health, Medical Research Council Biostatistics Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK
| | - Jon MacKay
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK.,Department of Anaesthesia and Intensive Care, Royal Papworth Hospital, Cambridge, UK
| | - Aman S Coonar
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
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19
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Williamson SF, Villar SS. A response-adaptive randomization procedure for multi-armed clinical trials with normally distributed outcomes. Biometrics 2019; 76:197-209. [PMID: 31322732 PMCID: PMC7078926 DOI: 10.1111/biom.13119] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 06/24/2019] [Indexed: 12/21/2022]
Abstract
We propose a novel response‐adaptive randomization procedure for multi‐armed trials with continuous outcomes that are assumed to be normally distributed. Our proposed rule is non‐myopic, and oriented toward a patient benefit objective, yet maintains computational feasibility. We derive our response‐adaptive algorithm based on the Gittins index for the multi‐armed bandit problem, as a modification of the method first introduced in Villar et al. (Biometrics, 71, pp. 969‐978). The resulting procedure can be implemented under the assumption of both known or unknown variance. We illustrate the proposed procedure by simulations in the context of phase II cancer trials. Our results show that, in a multi‐armed setting, there are efficiency and patient benefit gains of using a response‐adaptive allocation procedure with a continuous endpoint instead of a binary one. These gains persist even if an anticipated low rate of missing data due to deaths, dropouts, or complete responses is imputed online through a procedure first introduced in this paper. Additionally, we discuss how there are response‐adaptive designs that outperform the traditional equal randomized design both in terms of efficiency and patient benefit measures in the multi‐armed trial context.
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Affiliation(s)
- S Faye Williamson
- Department of Mathematics and Statistics, Lancaster University, Lancaster, UK.,MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - Sofía S Villar
- MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
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20
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Butchart AG, Zochios V, Villar SS, Jones NL, Curry S, Agrawal B, Jenkins DP, Klein AA. Measurement of extravascular lung water to diagnose severe reperfusion lung injury following pulmonary endarterectomy: a prospective cohort clinical validation study. Anaesthesia 2019; 74:1282-1289. [PMID: 31273760 PMCID: PMC6772184 DOI: 10.1111/anae.14744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2019] [Indexed: 11/28/2022]
Abstract
The measurement of extravascular lung water is a relatively new technology which has not yet been well validated as a clinically useful tool. We studied its utility in patients undergoing pulmonary endarterectomy as they frequently suffer reperfusion lung injury and associated oedematous lungs. Such patients are therefore ideal for evaluating this new monitor. We performed a prospective observational cohort study during which extravascular lung water index measurements were taken before and immediately after surgery and postoperatively in intensive care. Data were analysed for 57 patients; 21 patients (37%) experienced severe reperfusion lung injury. The first extravascular lung water index measurement after cardiopulmonary bypass failed to predict severe reperfusion lung injury, area under the receiver operating characteristic curve 0.59 (95%CI 0.44–0.74). On intensive care, extravascular lung water index correlated most strongly at 36 h, area under the receiver operating characteristic curve 0.90 (95%CI 0.80–1.00). Peri‐operative extravascular lung water index is not a useful measure to predict severe reperfusion lung injury after pulmonary endarterectomy, however, it does allow monitoring and measurement during the postoperative period. This study implies that extravascular lung water index can be used to directly assess pulmonary fluid overload and that monitoring patients by measuring extravascular lung water index during their intensive care stay is useful and correlates with their clinical course. This may allow directed, pre‐empted therapy to attenuate the effects and improve patient outcomes and should prompt further studies.
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Affiliation(s)
- A G Butchart
- Department of Cardiothoracic Anaesthesia and Intensive Care Medicine, Royal Papworth Hospital, Cambridge, UK
| | - V Zochios
- Department of Intensive Care Medicine, University Hospitals Birmingham National Health Service Foundation Trust, Queen Elizabeth Hospital Birmingham, University of Birmingham, UK
| | - S S Villar
- MRC Biostatistics Unit, University of Cambridge School of Clinical Medicine, Cambridge Institute of Public Health, UK
| | - N L Jones
- Department of Cardiothoracic Anaesthesia and Intensive Care Medicine, Royal Papworth Hospital, Cambridge, UK
| | - S Curry
- Department of Cardiothoracic Anaesthesia and Intensive Care Medicine, Royal Papworth Hospital, Cambridge, UK
| | - B Agrawal
- Department of Radiology, Royal Papworth Hospital, Cambridge, UK
| | - D P Jenkins
- Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, UK
| | - A A Klein
- Department of Cardiothoracic Anaesthesia and Intensive Care Medicine, Royal Papworth Hospital, Cambridge, UK
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21
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Chiu YD, Villar SS, Brand JW, Patteril MV, Morrice DJ, Clayton J, Mackay JH. Logistic early warning scores to predict death, cardiac arrest or unplanned intensive care unit re-admission after cardiac surgery. Anaesthesia 2019; 75:162-170. [PMID: 31270799 PMCID: PMC6954099 DOI: 10.1111/anae.14755] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2019] [Indexed: 01/05/2023]
Abstract
NHS England recently mandated that the National Early Warning Score of vital signs be used in all acute hospital trusts in the UK despite limited validation in the postoperative setting. We undertook a multicentre UK study of 13,631 patients discharged from intensive care after risk‐stratified cardiac surgery in four centres, all of which used VitalPACTM to electronically collect postoperative National Early Warning Score vital signs. We analysed 540,127 sets of vital signs to generate a logistic score, the discrimination of which we compared with the national additive score for the composite outcome of: in‐hospital death; cardiac arrest; or unplanned intensive care admission. There were 578 patients (4.2%) with an outcome that followed 4300 sets of observations (0.8%) in the preceding 24 h: 499 out of 578 (86%) patients had unplanned re‐admissions to intensive care. Discrimination by the logistic score was significantly better than the additive score. Respective areas (95%CI) under the receiver‐operating characteristic curve with 24‐h and 6‐h vital signs were: 0.779 (0.771–0.786) vs. 0.754 (0.746–0.761), p < 0.001; and 0.841 (0.829–0.853) vs. 0.813 (0.800–0.825), p < 0.001, respectively. Our proposed logistic Early Warning Score was better than the current National Early Warning Score at discriminating patients who had an event after cardiac surgery from those who did not.
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Affiliation(s)
- Y-D Chiu
- Department of Anaesthesia and Intensive Care, Royal Papworth Hospital, Cambridge, UK.,MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, UK
| | - S S Villar
- MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, UK
| | - J W Brand
- Department of Anaesthesia and Critical Care, James Cook University Hospital, Middlesbrough, UK
| | - M V Patteril
- Department of Anaesthesia and Critical Care, University Hospitals Coventry and Warwickshire, Coventry, UK
| | - D J Morrice
- Department of Anaesthesia and Critical Care, New Cross Hospital, Wolverhampton, UK
| | - J Clayton
- Department of Anaesthesia and Intensive Care, Royal Papworth Hospital, Cambridge, UK
| | - J H Mackay
- Department of Anaesthesia and Intensive Care, Royal Papworth Hospital, Cambridge, UK
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22
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Abstract
In a rare life-threatening disease setting the number of patients in the trial is a high proportion of all patients with the condition (if not all of them). Further, this number is usually not enough to guarantee the required statistical power to detect a treatment effect of a meaningful size. In such a context, the idea of prioritizing patient benefit over hypothesis testing as the goal of the trial can lead to a trial design that produces useful information to guide treatment, even if it does not do so with the standard levels of statistical confidence. The idealised model to consider such an optimal design of a clinical trial is known as a classic multi-armed bandit problem with a finite patient horizon and a patient benefit objective function. Such a design maximises patient benefit by balancing the learning and earning goals as data accumulates and given the patient horizon. On the other hand, optimally solving such a model has a very high computational cost (many times prohibitive) and more importantly, a cumbersome implementation, even for populations as small as a hundred patients. Several computationally feasible heuristic rules to address this problem have been proposed over the last 40 years in the literature. In this article we study a novel heuristic approach to solve it based on the reformulation of the problem as a Restless bandit problem and the derivation of its corresponding Whittle index rule. Such rule was recently proposed in the context of a clinical trial in Villar et al (2015). We perform extensive computational studies to compare through both exact value calculations and simulated values the performance of this rule, other index rules and simpler heuristics previously proposed in the literature. Our results suggest that for the two and three-armed case and a patient horizon less or equal than a hundred patients, all index rules are a priori practically identical in terms of the expected proportion of success attained when all arms start with a uniform prior. However, we find that a posteriori, for specific values of the parameters of interest, the index policies outperform the simpler rules in every instance and specially so in the case of many arms and a larger, though still relatively small, total number of patients with the diseases. The very good performance of bandit rules in terms of patient benefit (i.e. expected number of successes and mean number of patients allocated to the best arm, if it exists) makes them very appealing in context of the challenge posed by drug development for rare life threatening diseases.
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Affiliation(s)
- Sofía S Villar
- MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge Institute of Public Health, University Forvie Site, Robinson Way, Cambridge. UK. CB2 0SR
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23
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Pallmann P, Bedding AW, Choodari-Oskooei B, Dimairo M, Flight L, Hampson LV, Holmes J, Mander AP, Odondi L, Sydes MR, Villar SS, Wason JMS, Weir CJ, Wheeler GM, Yap C, Jaki T. Adaptive designs in clinical trials: why use them, and how to run and report them. BMC Med 2018; 16:29. [PMID: 29490655 PMCID: PMC5830330 DOI: 10.1186/s12916-018-1017-7] [Citation(s) in RCA: 328] [Impact Index Per Article: 54.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 01/30/2018] [Indexed: 12/11/2022] Open
Abstract
Adaptive designs can make clinical trials more flexible by utilising results accumulating in the trial to modify the trial's course in accordance with pre-specified rules. Trials with an adaptive design are often more efficient, informative and ethical than trials with a traditional fixed design since they often make better use of resources such as time and money, and might require fewer participants. Adaptive designs can be applied across all phases of clinical research, from early-phase dose escalation to confirmatory trials. The pace of the uptake of adaptive designs in clinical research, however, has remained well behind that of the statistical literature introducing new methods and highlighting their potential advantages. We speculate that one factor contributing to this is that the full range of adaptations available to trial designs, as well as their goals, advantages and limitations, remains unfamiliar to many parts of the clinical community. Additionally, the term adaptive design has been misleadingly used as an all-encompassing label to refer to certain methods that could be deemed controversial or that have been inadequately implemented.We believe that even if the planning and analysis of a trial is undertaken by an expert statistician, it is essential that the investigators understand the implications of using an adaptive design, for example, what the practical challenges are, what can (and cannot) be inferred from the results of such a trial, and how to report and communicate the results. This tutorial paper provides guidance on key aspects of adaptive designs that are relevant to clinical triallists. We explain the basic rationale behind adaptive designs, clarify ambiguous terminology and summarise the utility and pitfalls of adaptive designs. We discuss practical aspects around funding, ethical approval, treatment supply and communication with stakeholders and trial participants. Our focus, however, is on the interpretation and reporting of results from adaptive design trials, which we consider vital for anyone involved in medical research. We emphasise the general principles of transparency and reproducibility and suggest how best to put them into practice.
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Affiliation(s)
- Philip Pallmann
- Department of Mathematics & Statistics, Lancaster University, Lancaster, LA1 4YF UK
| | | | - Babak Choodari-Oskooei
- MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, University College London, London, UK
| | | | - Laura Flight
- Medical Statistics Group, University of Sheffield, Sheffield, UK
| | - Lisa V. Hampson
- Department of Mathematics & Statistics, Lancaster University, Lancaster, LA1 4YF UK
- Statistical Innovation Group, Advanced Analytics Centre, AstraZeneca, Cambridge, UK
| | - Jane Holmes
- Centre for Statistics in Medicine, University of Oxford, Oxford, UK
| | | | - Lang’o Odondi
- Centre for Statistics in Medicine, University of Oxford, Oxford, UK
| | - Matthew R. Sydes
- MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, University College London, London, UK
| | - Sofía S. Villar
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
| | - James M. S. Wason
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
- Institute of Health and Society, Newcastle University, Newcastle, UK
| | - Christopher J. Weir
- Usher Institute of Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, UK
| | - Graham M. Wheeler
- MRC Biostatistics Unit, University of Cambridge, Cambridge, UK
- Cancer Research UK & UCL Cancer Trials Centre, University College London, London, UK
| | - Christina Yap
- Cancer Research UK Clinical Trials Unit, University of Birmingham, Birmingham, UK
| | - Thomas Jaki
- Department of Mathematics & Statistics, Lancaster University, Lancaster, LA1 4YF UK
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24
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Villar SS, Bowden J, Wason J. Response-adaptive designs for binary responses: How to offer patient benefit while being robust to time trends? Pharm Stat 2017; 17:182-197. [PMID: 29266692 PMCID: PMC5877788 DOI: 10.1002/pst.1845] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/27/2017] [Accepted: 11/07/2017] [Indexed: 12/15/2022]
Abstract
Response‐adaptive randomisation (RAR) can considerably improve the chances of a successful treatment outcome for patients in a clinical trial by skewing the allocation probability towards better performing treatments as data accumulates. There is considerable interest in using RAR designs in drug development for rare diseases, where traditional designs are not either feasible or ethically questionable. In this paper, we discuss and address a major criticism levelled at RAR: namely, type I error inflation due to an unknown time trend over the course of the trial. The most common cause of this phenomenon is changes in the characteristics of recruited patients—referred to as patient drift. This is a realistic concern for clinical trials in rare diseases due to their lengthly accrual rate. We compute the type I error inflation as a function of the time trend magnitude to determine in which contexts the problem is most exacerbated. We then assess the ability of different correction methods to preserve type I error in these contexts and their performance in terms of other operating characteristics, including patient benefit and power. We make recommendations as to which correction methods are most suitable in the rare disease context for several RAR rules, differentiating between the 2‐armed and the multi‐armed case. We further propose a RAR design for multi‐armed clinical trials, which is computationally efficient and robust to several time trends considered.
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Affiliation(s)
- Sofía S Villar
- MRC Biostatistics Unit, Cambridge Institute of Public Health, Cambridge, UK
| | - Jack Bowden
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
| | - James Wason
- MRC Biostatistics Unit, Cambridge Institute of Public Health, Cambridge, UK
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25
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Villar SS, Rosenberger WF. Covariate-adjusted response-adaptive randomization for multi-arm clinical trials using a modified forward looking Gittins index rule. Biometrics 2017; 74:49-57. [PMID: 28682442 PMCID: PMC6055987 DOI: 10.1111/biom.12738] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 04/01/2017] [Accepted: 05/01/2017] [Indexed: 11/29/2022]
Abstract
We introduce a non-myopic, covariate-adjusted response adaptive (CARA) allocation design for multi-armed clinical trials. The allocation scheme is a computationally tractable procedure based on the Gittins index solution to the classic multi-armed bandit problem and extends the procedure recently proposed in Villar et al. (2015). Our proposed CARA randomization procedure is defined by reformulating the bandit problem with covariates into a classic bandit problem in which there are multiple combination arms, considering every arm per each covariate category as a distinct treatment arm. We then apply a heuristically modified Gittins index rule to solve the problem and define allocation probabilities from the resulting solution. We report the efficiency, balance, and ethical performance of our approach compared to existing CARA methods using a recently published clinical trial as motivation. The net savings in terms of expected number of treatment failures is considerably larger and probably enough to make this design attractive for certain studies where known covariates are expected to be important, stratification is not desired, treatment failures have a high ethical cost, and the disease under study is rare. In a two-armed context, this patient benefit advantage comes at the expense of increased variability in the allocation proportions and a reduction in statistical power. However, in a multi-armed context, simple modifications of the proposed CARA rule can be incorporated so that an ethical advantage can be offered without sacrificing power in comparison with balanced designs.
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Affiliation(s)
- Sofía S Villar
- MRC Biostatistics Unit, School of Clinical Medicine, University of Cambridge, Cambridge, U.K
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26
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Abstract
Adaptive designs for multi-armed clinical trials have become increasingly popular recently because of their potential to shorten development times and to increase patient response. However, developing response-adaptive designs that offer patient-benefit while ensuring the resulting trial provides a statistically rigorous and unbiased comparison of the different treatments included is highly challenging. In this paper, the theory of Multi-Armed Bandit Problems is used to define near optimal adaptive designs in the context of a clinical trial with a normally distributed endpoint with known variance. We report the operating characteristics (type I error, power, bias) and patient-benefit of these approaches and alternative designs using simulation studies based on an ongoing trial. These results are then compared to those recently published in the context of Bernoulli endpoints. Many limitations and advantages are similar in both cases but there are also important differences, specially with respect to type I error control. This paper proposes a simulation-based testing procedure to correct for the observed type I error inflation that bandit-based and adaptive rules can induce.
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Affiliation(s)
- Adam L Smith
- Department of Pure Mathematics and Mathematical Statistics, University of Cambridge, Cambridge, UK
| | - Sofía S Villar
- MRC Biostatistics Unit, University of Cambridge, School of Clinical Medicine, Cambridge, UK
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27
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Abstract
Development of treatments for rare diseases is challenging due to the limited number of patients available for participation. Learning about treatment effectiveness with a view to treat patients in the larger outside population, as in the traditional fixed randomised design, may not be a plausible goal. An alternative goal is to treat the patients within the trial as effectively as possible. Using the framework of finite-horizon Markov decision processes and dynamic programming (DP), a novel randomised response-adaptive design is proposed which maximises the total number of patient successes in the trial and penalises if a minimum number of patients are not recruited to each treatment arm. Several performance measures of the proposed design are evaluated and compared to alternative designs through extensive simulation studies using a recently published trial as motivation. For simplicity, a two-armed trial with binary endpoints and immediate responses is considered. Simulation results for the proposed design show that: (i) the percentage of patients allocated to the superior arm is much higher than in the traditional fixed randomised design; (ii) relative to the optimal DP design, the power is largely improved upon and (iii) it exhibits only a very small bias and mean squared error of the treatment effect estimator. Furthermore, this design is fully randomised which is an advantage from a practical point of view because it protects the trial against various sources of bias. As such, the proposed design addresses some of the key issues that have been suggested as preventing so-called bandit models from being implemented in clinical practice.
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Affiliation(s)
| | - Peter Jacko
- Department of Management Science, Lancaster University, UK
| | | | - Thomas Jaki
- Department of Mathematics and Statistics, Lancaster University, UK
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28
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Abstract
Motivated by a class of Partially Observable Markov Decision Processes with application in surveillance systems in which a set of imperfectly observed state processes is to be inferred from a subset of available observations through a Bayesian approach, we formulate and analyze a special family of multi-armed restless bandit problems. We consider the problem of finding an optimal policy for observing the processes that maximizes the total expected net rewards over an infinite time horizon subject to the resource availability. From the Lagrangian relaxation of the original problem, an index policy can be derived, as long as the existence of the Whittle index is ensured. We demonstrate that such a class of reinitializing bandits in which the projects' state deteriorates while active and resets to its initial state when passive until its completion possesses the structural property of indexability and we further show how to compute the index in closed form. In general, the Whittle index rule for restless bandit problems does not achieve optimality. However, we show that the proposed Whittle index rule is optimal for the problem under study in the case of stochastically heterogenous arms under the expected total criterion, and it is further recovered by a simple tractable rule referred to as the 1-limited Round Robin rule. Moreover, we illustrate the significant suboptimality of other widely used heuristic: the Myopic index rule, by computing in closed form its suboptimality gap. We present numerical studies which illustrate for the more general instances the performance advantages of the Whittle index rule over other simple heuristics.
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Affiliation(s)
- Sofía S Villar
- BCAM, Basque Center for Applied Mathematics and MRC Biostatistics Unit, IPH, University Forvie Site, Robinson Way, Cambridge CB2 0SR, UK and Lancaster University,
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29
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Villar SS, Wason J, Bowden J. Response-adaptive randomization for multi-arm clinical trials using the forward looking Gittins index rule. Biometrics 2015; 71:969-78. [PMID: 26098023 DOI: 10.1111/biom.12337] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 03/01/2015] [Accepted: 04/01/2015] [Indexed: 11/27/2022]
Abstract
The Gittins index provides a well established, computationally attractive, optimal solution to a class of resource allocation problems known collectively as the multi-arm bandit problem. Its development was originally motivated by the problem of optimal patient allocation in multi-arm clinical trials. However, it has never been used in practice, possibly for the following reasons: (1) it is fully sequential, i.e., the endpoint must be observable soon after treating a patient, reducing the medical settings to which it is applicable; (2) it is completely deterministic and thus removes randomization from the trial, which would naturally protect against various sources of bias. We propose a novel implementation of the Gittins index rule that overcomes these difficulties, trading off a small deviation from optimality for a fully randomized, adaptive group allocation procedure which offers substantial improvements in terms of patient benefit, especially relevant for small populations. We report the operating characteristics of our approach compared to existing methods of adaptive randomization using a recently published trial as motivation.
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Affiliation(s)
- Sofía S Villar
- MRC Biostatistics Unit, Institute of Public Health, University Forvie Site, Robinson Way, Cambridge CB2 0SR, U.K.,Department of Mathematics and Statistics, Lancaster University, Bailrigg, Lancaster LA1 4YW, U.K
| | - James Wason
- MRC Biostatistics Unit, Institute of Public Health, University Forvie Site, Robinson Way, Cambridge CB2 0SR, U.K
| | - Jack Bowden
- MRC Biostatistics Unit, Institute of Public Health, University Forvie Site, Robinson Way, Cambridge CB2 0SR, U.K
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30
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Abstract
Multi-armed bandit problems (MABPs) are a special type of optimal control problem well suited to model resource allocation under uncertainty in a wide variety of contexts. Since the first publication of the optimal solution of the classic MABP by a dynamic index rule, the bandit literature quickly diversified and emerged as an active research topic. Across this literature, the use of bandit models to optimally design clinical trials became a typical motivating application, yet little of the resulting theory has ever been used in the actual design and analysis of clinical trials. To this end, we review two MABP decision-theoretic approaches to the optimal allocation of treatments in a clinical trial: the infinite-horizon Bayesian Bernoulli MABP and the finite-horizon variant. These models possess distinct theoretical properties and lead to separate allocation rules in a clinical trial design context. We evaluate their performance compared to other allocation rules, including fixed randomization. Our results indicate that bandit approaches offer significant advantages, in terms of assigning more patients to better treatments, and severe limitations, in terms of their resulting statistical power. We propose a novel bandit-based patient allocation rule that overcomes the issue of low power, thus removing a potential barrier for their use in practice.
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Affiliation(s)
- Sofía S. Villar
- Investigator Statistician at MRC BSU, Cambridge and Biometrika post-doctoral research fellow
| | - Jack Bowden
- Senior Investigator Statistician at MRC BSU, Cambridge
| | - James Wason
- Senior Investigator Statistician at MRC BSU, Cambridge, MRC Biostatistics Unit, Cambridge Institute of Public Health, Forvie Site, Robinson Way, Cambridge Biomedical Campus, Cambridge CB2 0SR, United Kingdom
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