1
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Ocampo A, Bather JR. Single-world intervention graphs for defining, identifying, and communicating estimands in clinical trials. Stat Med 2023; 42:3892-3902. [PMID: 37340887 DOI: 10.1002/sim.9833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 05/17/2023] [Accepted: 06/01/2023] [Indexed: 06/22/2023]
Abstract
Confusion often arises when attempting to articulate target estimand(s) of a clinical trial in plain language. We aim to rectify this confusion by using a type of causal graph called the Single-World Intervention Graph (SWIG) to provide a visual representation of the estimand that can be effectively communicated to interdisciplinary stakeholders. These graphs not only display estimands, but also illustrate the assumptions under which a causal estimand is identifiable by presenting the graphical relationships between the treatment, intercurrent events, and clinical outcomes. To demonstrate its usefulness in pharmaceutical research, we present examples of SWIGs for various intercurrent event strategies specified in the ICH E9(R1) addendum, as well as an example from a real-world clinical trial for chronic pain. code to generate all the SWIGs shown is this paper is made available. We advocate clinical trialists adopt the use of SWIGs in their estimand discussions during the planning stages of their studies.
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Affiliation(s)
- Alex Ocampo
- Neuroscience Biostatistics Division, Novartis Pharma AG, Basel, Switzerland
| | - Jemar R Bather
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
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2
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David S, Bode C, Stahl K. EXCHANGE-2: investigating the efficacy of add-on plasma exchange as an adjunctive strategy against septic shock-a study protocol for a randomized, prospective, multicenter, open-label, controlled, parallel-group trial. Trials 2023; 24:277. [PMID: 37061693 PMCID: PMC10105400 DOI: 10.1186/s13063-023-07300-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/05/2023] [Indexed: 04/17/2023] Open
Abstract
BACKGROUND Sepsis is as a life-threatening organ dysfunction caused by a dysregulated host response to an infection. The mortality of sepsis and particular of septic shock is very high. Treatment mostly focuses on infection control but a specific intervention that targets the underlying pathological host response is lacking to the present time. The investigators hypothesize that early therapeutic plasma exchange (TPE) will dampen the maladaptive host response by removing injurious mediators thereby limiting organ dysfunction and improving survival in patients with septic shock. Although small prospective studies demonstrated rapid hemodynamic stabilization under TPE, no adequately powered randomized clinical trial has investigated hard outcomes. METHODS This is a randomized, prospective, multicenter, open-label, controlled, parallel-group interventional trial to test the adjunctive effect of TPE in patients with early septic shock. Patients with a refractory (defined as norepinephrine (NE) ≥ 0.4 μg/kg/min ≥ 30 min OR NE 0.3 μg/kg/min + vasopressin) and early (shock onset < 24 h) septic shock will be included. The intervention is a standard TPE with donor fresh frozen plasma (1.2 × individual plasma volume) performed within 6 h after randomization and will be compared to a standard of care (SOC) control arm. The primary endpoint is 28 days mortality for which the power analysis revealed a group size of 137 / arm (n = 274) to demonstrate a benefit of 15%. The key secondary objective will be to compare the extent of organ failure indicated by mean SOFA over the first 7 days as well as organ support-free days until day 28 following randomization. Besides numerous biological secondary, safety endpoints such as incidence of bleeding, allergic reactions, transfusion associated lung injury, severe thrombocytopenia, and other severe adverse events will be assessed during the first 7 days. For exploratory scientific analyses, biomaterial will be acquired longitudinally and multiple predefined scientific subprojects are planned. This study is an investigator-initiated trial supported by the German Research Foundation (DFG, DA 1209/7-1), in which 26 different centers in Germany, Switzerland, and Austria will participate over a duration of 33 months. DISCUSSION This trial has substantial clinical relevance as it evaluates a promising adjunctive treatment option in refractory septic shock patients suffering from an extraordinary high mortality. A positive trial result could change the current standard of care for this septic subgroup. The results of this study will be disseminated through presentations at international congresses, workshops, and peer-reviewed publications. TRIAL REGISTRATION ClinicalTrials.gov NCT05726825 , Registered on 14 February 2023.
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Affiliation(s)
- Sascha David
- Institute of Intensive Care Medicine, University Hospital Zurich, Rämistrasse 100, 8091, Zurich, Switzerland.
- Department of Nephrology and Hypertension, Hannover Medical School, Hannover, Germany.
| | - Christian Bode
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany
| | - Klaus Stahl
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
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3
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Lipkovich I, Ratitch B, Qu Y, Zhang X, Shan M, Mallinckrodt C. Using principal stratification in analysis of clinical trials. Stat Med 2022; 41:3837-3877. [PMID: 35851717 DOI: 10.1002/sim.9439] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 03/06/2022] [Accepted: 05/03/2022] [Indexed: 11/08/2022]
Abstract
The ICH E9(R1) addendum (2019) proposed principal stratification (PS) as one of five strategies for dealing with intercurrent events. Therefore, understanding the strengths, limitations, and assumptions of PS is important for the broad community of clinical trialists. Many approaches have been developed under the general framework of PS in different areas of research, including experimental and observational studies. These diverse applications have utilized a diverse set of tools and assumptions. Thus, need exists to present these approaches in a unifying manner. The goal of this tutorial is threefold. First, we provide a coherent and unifying description of PS. Second, we emphasize that estimation of effects within PS relies on strong assumptions and we thoroughly examine the consequences of these assumptions to understand in which situations certain assumptions are reasonable. Finally, we provide an overview of a variety of key methods for PS analysis and use a real clinical trial example to illustrate them. Examples of code for implementation of some of these approaches are given in Supplemental Materials.
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Affiliation(s)
| | | | - Yongming Qu
- Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Xiang Zhang
- CSL Behring, King of Prussia, Pennsylvania, USA
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4
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Jin M. A hybrid return to baseline imputation method to incorporate MAR and MNAR dropout missingness. Contemp Clin Trials 2022; 120:106859. [PMID: 35872135 DOI: 10.1016/j.cct.2022.106859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 07/07/2022] [Accepted: 07/15/2022] [Indexed: 11/03/2022]
Abstract
Missing data are inevitable in longitudinal clinical trials due to intercurrent events (ICEs) such as treatment interruption or premature discontinuation for different reasons. Missing at random (MAR) assumption is usually unverifiable and sensitivity analyses are often requested under missing not at random (MNAR) assumption. Return to baseline (RTB) imputation is a commonly used MNAR method. In practice, not all dropout missingness can be assumed MNAR. For example, missingness or dropouts due to COVID-19 can be reasonably assumed MAR. Therefore, traditional RTB is not applicable when there is both MAR and MNAR dropout missingness. Here we propose a hybrid strategy for RTB imputation which can handle missing data due to MAR and MNAR dropouts at the same time. Standard multiple imputation approach is proposed and an analytic likelihood based approach is derived to improve efficiency.
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Affiliation(s)
- Man Jin
- Data and Statistical Sciences, AbbVie Inc., North Chicago, IL 60064, USA.
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5
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Wang S, Hu H. Impute the missing data using retrieved dropouts. BMC Med Res Methodol 2022; 22:82. [PMID: 35350976 PMCID: PMC8962050 DOI: 10.1186/s12874-022-01509-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 01/11/2022] [Indexed: 11/10/2022] Open
Abstract
Background In the past few decades various methods have been proposed to handle missing data of clinical studies, so as to assess the robustness of primary results. Some of the methods are based on the assumption of missing at random (MAR) which assumes subjects who discontinue the treatment will maintain the treatment effect after discontinuation. The agency, however, has expressed concern over methods based on this overly optimistic assumption, because it hardly holds for subjects discontinuing the investigational drug. Although in recent years a good number of sensitivity analyses based on missing not at random (MNAR) assumptions have been proposed, some use very conservative assumption on which it might be hard for sponsors and regulators to reach common ground. Methods Here we propose a multiple imputation method targeting at “treatment policy” estimand based on the MNAR assumption. This method can be used as the primary analysis, in addition to serving as a sensitivity analysis. It imputes missing data using information from retrieved dropouts defined as subjects who remain in the study despite occurrence of intercurrent events. Then imputed data long with completers and retrieved dropouts are analyzed altogether and finally multiple results are summarized into a single estimate. According to definition in ICH E9 (R1), this proposed approach fully aligns with the treatment policy estimand but its assumption is much more realistic and reasonable. Results Our approach has well controlled type I error rate with no loss of power. As expected, the effect size estimates take into account any dilution effect contributed by retrieved dropouts, conforming to the MNAR assumption. Conclusions Although multiple imputation approaches are always used as sensitivity analyses, this multiple imputation approach can be used as primary analysis for trials with sufficient retrieved dropouts or trials designed to collect retrieved dropouts. Supplementary Information The online version contains supplementary material available at 10.1186/s12874-022-01509-9.
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Affiliation(s)
- Shuai Wang
- Global Product Development, Pfizer Inc, Groton, CT, 06340, USA.
| | - Haoyan Hu
- Department of Statistics, Iowa State University, Ames, IA, 50011, USA
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6
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Hazewinkel A, Bowden J, Wade KH, Palmer T, Wiles NJ, Tilling K. Sensitivity to missing not at random dropout in clinical trials: Use and interpretation of the trimmed means estimator. Stat Med 2022; 41:1462-1481. [PMID: 35098576 PMCID: PMC9303448 DOI: 10.1002/sim.9299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 12/09/2021] [Accepted: 12/11/2021] [Indexed: 11/17/2022]
Abstract
Outcome values in randomized controlled trials (RCTs) may be missing not at random (MNAR), if patients with extreme outcome values are more likely to drop out (eg, due to perceived ineffectiveness of treatment, or adverse effects). In such scenarios, estimates from complete case analysis (CCA) and multiple imputation (MI) will be biased. We investigate the use of the trimmed means (TM) estimator for the case of univariable missingness in one continuous outcome. The TM estimator operates by setting missing values to the most extreme value, and then “trimming” away equal fractions of both groups, estimating the treatment effect using the remaining data. The TM estimator relies on two assumptions, which we term the “strong MNAR” and “location shift” assumptions. We derive formulae for the TM estimator bias resulting from the violation of these assumptions for normally distributed outcomes. We propose an adjusted TM estimator, which relaxes the location shift assumption and detail how our bias formulae can be used to establish the direction of bias of CCA and TM estimates, to inform sensitivity analyses. The TM approach is illustrated in a sensitivity analysis of the CoBalT RCT of cognitive behavioral therapy (CBT) in 469 individuals with 46 months follow‐up. Results were consistent with a beneficial CBT treatment effect, with MI estimates closer to the null and TM estimates further from the null than the CCA estimate. We propose using the TM estimator as a sensitivity analysis for data where extreme outcome value dropout is plausible.
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Affiliation(s)
- Audinga‐Dea Hazewinkel
- Population Health Sciences, Bristol Medical School University of Bristol Bristol UK
- Medical Research Council Integrative Epidemiology Unit, Bristol Medical School University of Bristol Bristol UK
| | - Jack Bowden
- Medical Research Council Integrative Epidemiology Unit, Bristol Medical School University of Bristol Bristol UK
- Exeter Diabetes Group (ExCEED), College of Medicine and Health University of Exeter Exeter UK
| | - Kaitlin H. Wade
- Population Health Sciences, Bristol Medical School University of Bristol Bristol UK
- Medical Research Council Integrative Epidemiology Unit, Bristol Medical School University of Bristol Bristol UK
| | - Tom Palmer
- Population Health Sciences, Bristol Medical School University of Bristol Bristol UK
- Medical Research Council Integrative Epidemiology Unit, Bristol Medical School University of Bristol Bristol UK
| | - Nicola J. Wiles
- Centre for Academic Mental Health, Population Health Sciences, Bristol Medical School University of Bristol Bristol UK
| | - Kate Tilling
- Population Health Sciences, Bristol Medical School University of Bristol Bristol UK
- Medical Research Council Integrative Epidemiology Unit, Bristol Medical School University of Bristol Bristol UK
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7
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Bowden J, Bornkamp B, Glimm E, Bretz F. Connecting Instrumental Variable methods for causal inference to the Estimand Framework. Stat Med 2021; 40:5605-5627. [PMID: 34288021 DOI: 10.1002/sim.9143] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 07/01/2021] [Accepted: 07/02/2021] [Indexed: 11/09/2022]
Abstract
Causal inference methods are gaining increasing prominence in pharmaceutical drug development in light of the recently published addendum on estimands and sensitivity analysis in clinical trials to the E9 guideline of the International Council for Harmonisation. The E9 addendum emphasises the need to account for post-randomization or 'intercurrent' events that can potentially influence the interpretation of a treatment effect estimate at a trial's conclusion. Instrumental Variables (IV) methods have been used extensively in economics, epidemiology, and academic clinical studies for 'causal inference,' but less so in the pharmaceutical industry setting until now. In this tutorial article we review the basic tools for causal inference, including graphical diagrams and potential outcomes, as well as several conceptual frameworks that an IV analysis can sit within. We discuss in detail how to map these approaches to the Treatment Policy, Principal Stratum and Hypothetical 'estimand strategies' introduced in the E9 addendum, and provide details of their implementation using standard regression models. Specific attention is given to discussing the assumptions each estimation strategy relies on in order to be consistent, the extent to which they can be empirically tested and sensitivity analyses in which specific assumptions can be relaxed. We finish by applying the methods described to simulated data closely matching two recent pharmaceutical trials to further motivate and clarify the ideas.
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Affiliation(s)
- Jack Bowden
- Exeter Diabetes Group (ExCEED), College of Medicine and Health, University of Exeter, Exeter, UK.,MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
| | | | - Ekkehard Glimm
- Novartis Pharma AG, Basel, Switzerland.,Institute for Biometry and Medical Informatics, Medical Faculty, University of Magdeburg, Magdeburg, Germany
| | - Frank Bretz
- Novartis Pharma AG, Basel, Switzerland.,Section for Medical Statistics, Medical University of Vienna, Vienna, Austria
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8
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Ocampo A, Schmidli H, Quarg P, Callegari F, Pagano M. Identifying treatment effects using trimmed means when data are missing not at random. Pharm Stat 2021; 20:1265-1277. [PMID: 34169641 DOI: 10.1002/pst.2147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 05/28/2021] [Accepted: 06/01/2021] [Indexed: 11/06/2022]
Abstract
Patients often discontinue from a clinical trial because their health condition is not improving or they cannot tolerate the assigned treatment. Consequently, the observed clinical outcomes in the trial are likely better on average than if every patient had completed the trial. If these differences between trial completers and non-completers cannot be explained by the observed data, then the study outcomes are missing not at random (MNAR). One way to overcome this problem-the trimmed means approach for missing data due to study discontinuation-sets missing values as the worst observed outcome and then trims away a fraction of the distribution from each treatment arm before calculating differences in treatment efficacy (Permutt T, Li F. Trimmed means for symptom trials with dropouts. Pharm Stat. 2017;16(1):20-28). In this paper, we derive sufficient and necessary conditions for when this approach can identify the average population treatment effect. Simulation studies show the trimmed means approach's ability to effectively estimate treatment efficacy when data are MNAR and missingness due to study discontinuation is strongly associated with an unfavorable outcome, but trimmed means fail when data are missing at random. If the reasons for study discontinuation in a clinical trial are known, analysts can improve estimates with a combination of multiple imputation and the trimmed means approach when the assumptions of each hold. We compare the methodology to existing approaches using data from a clinical trial for chronic pain. An R package trim implements the method. When the assumptions are justifiable, using trimmed means can help identify treatment effects notwithstanding MNAR data.
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Affiliation(s)
- Alex Ocampo
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | | | | | | | - Marcello Pagano
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
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9
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Estimands and missing data in clinical trials of chronic pain treatments: advances in design and analysis. Pain 2021; 161:2308-2320. [PMID: 32453131 DOI: 10.1097/j.pain.0000000000001937] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In clinical trials of treatments for chronic pain, the percentage of participants who withdraw early can be as high as 50%. Major reasons for early withdrawal in these studies include perceived lack of efficacy and adverse events. Commonly used strategies for accommodating missing data include last observation carried forward, baseline observation carried forward, and more principled methods such as mixed-model repeated-measures and multiple imputation. All these methods require strong and untestable assumptions concerning the conditional distribution of outcomes after dropout, given the observed data. We review recent developments in statistical methods for handling missing data in clinical trials, including implications of the increased emphasis being placed on precise formulation of the study objectives and the estimand (treatment effect to be estimated) of interest. A flexible method that seems to be well suited for the analysis of chronic pain clinical trials is control-based imputation, which allows a variety of assumptions to be made concerning the conditional distribution of postdropout outcomes that can be tailored to the estimand of interest. These assumptions can depend, for example, on the stated reasons for dropout. We illustrate these methods using data from 4 clinical trials of pregabalin for the treatment of painful diabetic peripheral neuropathy and postherpetic neuralgia. When planning chronic pain clinical trials, careful consideration of the trial objectives should determine the definition of the trial estimand, which in turn should inform methods used to accommodate missing data in the statistical analysis.
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10
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Essential statistical principles of clinical trials of pain treatments. Pain Rep 2020; 6:e863. [PMID: 33521483 PMCID: PMC7837867 DOI: 10.1097/pr9.0000000000000863] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/08/2020] [Accepted: 09/09/2020] [Indexed: 01/13/2023] Open
Abstract
This article presents an overview of fundamental statistical principles of clinical trials of pain treatments. Statistical considerations relevant to phase 2 proof of concept and phase 3 confirmatory randomized trials investigating efficacy and safety are discussed, including (1) research design; (2) endpoints and analyses; (3) sample size determination and statistical power; (4) missing data and trial estimands; (5) data monitoring and interim analyses; and (6) interpretation of results. Although clinical trials of pharmacologic treatments are emphasized, the key issues raised by these trials are also directly applicable to clinical trials of other types of treatments, including biologics, devices, nonpharmacologic therapies (eg, physical therapy and cognitive-behavior therapy), and complementary and integrative health interventions.
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11
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Darken P, Nyberg J, Ballal S, Wright D. The attributable estimand: A new approach to account for intercurrent events. Pharm Stat 2020; 19:626-635. [PMID: 32198954 DOI: 10.1002/pst.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 12/30/2019] [Accepted: 03/02/2020] [Indexed: 11/08/2022]
Abstract
The term "intercurrent events" has recently been used to describe events in clinical trials that may complicate the definition and calculation of the treatment effect estimand. This paper focuses on the use of an attributable estimand to address intercurrent events. Those events that are considered to be adversely related to randomized treatment (eg, discontinuation due to adverse events or lack of efficacy) are considered attributable and handled with a composite estimand strategy, while a hypothetical estimand strategy is used for intercurrent events not considered to be related to randomized treatment (eg, unrelated adverse events). We explore several options for how to implement this approach and compare them to hypothetical "efficacy" and treatment policy estimand strategies through a series of simulation studies whose design is inspired by recent trials in chronic obstructive pulmonary disease (COPD), and we illustrate through an analysis of a recently completed COPD trial.
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12
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Lipkovich I, Ratitch B, Mallinckrodt CH. Causal Inference and Estimands in Clinical Trials. Stat Biopharm Res 2020. [DOI: 10.1080/19466315.2019.1697739] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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13
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Liu GF, Liu F, Mehrotra DV. Model Averaging Using Likelihoods That Reflect Poor Outcomes for Clinical Trial Dropouts. Stat Biopharm Res 2020. [DOI: 10.1080/19466315.2019.1697740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
| | - Fang Liu
- Merck & Co., Inc, North Wales, PA
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14
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Keene ON, Ruberg S, Schacht A, Akacha M, Lawrance R, Berglind A, Wright D. What matters most? Different stakeholder perspectives on estimands for an invented case study in COPD. Pharm Stat 2020; 19:370-387. [DOI: 10.1002/pst.1986] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 08/16/2019] [Accepted: 10/23/2019] [Indexed: 12/11/2022]
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15
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Rockhold FW, Lindblad A, Siegel JP, Molenberghs G. University of Pennsylvania 11th annual conference on statistical issues in clinical trials: Estimands, missing data and sensitivity analysis (morning panel session). Clin Trials 2019; 16:350-362. [PMID: 31303021 DOI: 10.1177/1740774519853573] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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16
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17
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Abstract
In this article, I review the key elements of the proposed International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use E9 Addendum, present a constructive critique, and provide recommendations of how it can be improved. To highlight ideas, I present a case study involving a confirmatory trial for a chronic pain medication.
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Affiliation(s)
- Daniel O Scharfstein
- Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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18
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Affiliation(s)
- Lisa M. LaVange
- Department of Biostatistics, University of North Carolina at Chapel Hill, NC
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19
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Bell ML, Floden L, Rabe BA, Hudgens S, Dhillon HM, Bray VJ, Vardy JL. Analytical approaches and estimands to take account of missing patient-reported data in longitudinal studies. PATIENT-RELATED OUTCOME MEASURES 2019; 10:129-140. [PMID: 31114411 PMCID: PMC6489631 DOI: 10.2147/prom.s178963] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 03/14/2019] [Indexed: 11/30/2022]
Abstract
Patient-reported outcomes, such as quality of life, functioning, and symptoms, are used widely in therapeutic and behavioral trials and are increasingly used in drug development to represent the patient voice. Missing patient reported data is common and can undermine the validity of results reporting by reducing power, biasing estimates, and ultimately reducing confidence in the results. In this paper, we review statistically principled approaches for handling missing patient-reported outcome data and introduce the idea of estimands in the context of behavioral trials. Specifically, we outline a plan that considers missing data at each stage of research: design, data collection, analysis, and reporting. The design stage includes processes to prevent missing data, define the estimand, and specify primary and sensitivity analyses. The analytic strategy considering missing data depends on the estimand. Reviewed approaches include maximum likelihood-based models, multiple imputation, generalized estimating equations, and responder analysis. We outline sensitivity analyses to assess the robustness of the primary analysis results when data are missing. We also describe ad-hoc methods, including approaches to avoid. Last, we demonstrate methods using data from a behavioral intervention, where the primary outcome was self-reported cognition.
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Affiliation(s)
- Melanie L Bell
- Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ 85724, USA.,Psycho-Oncology Co-operative Research Group, School of Psychology, University of Sydney, Sydney, NSW, Australia
| | - Lysbeth Floden
- Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ 85724, USA.,Clinical Outcomes Solutions, Tucson, AZ 85718, USA
| | - Brooke A Rabe
- Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ 85724, USA
| | | | - Haryana M Dhillon
- Psycho-Oncology Co-operative Research Group, School of Psychology, University of Sydney, Sydney, NSW, Australia.,Centre for Medical Psychology & Evidence-Based Decision-Making, School of Psychology, University of Sydney, Sydney, NSW, Australia
| | - Victoria J Bray
- Department of Medical Oncology, Liverpool Hospital and University of Sydney, Sydney, NSW, Australia
| | - Janette L Vardy
- Concord Cancer Centre and Sydney Medical School, University of Sydney, Sydney, NSW, Australia
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20
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Ratitch B, Goel N, Mallinckrodt C, Bell J, Bartlett JW, Molenberghs G, Singh P, Lipkovich I, O’Kelly M. Defining Efficacy Estimands in Clinical Trials: Examples Illustrating ICH E9(R1) Guidelines. Ther Innov Regul Sci 2019. [DOI: 10.1177/2168479019841316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
| | - Niti Goel
- Kezar Life Sciences, South San Francisco, CA, USA
- Department of Medicine, Duke University School of Medicine, Durham, NC, USA
| | | | - James Bell
- Elderbrook Solutions GmbH, High Wycombe, United Kingdom
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21
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Mallinckrodt CH, Bell J, Liu G, Ratitch B, O’Kelly M, Lipkovich I, Singh P, Xu L, Molenberghs G. Aligning Estimators With Estimands in Clinical Trials: Putting the ICH E9(R1) Guidelines Into Practice. Ther Innov Regul Sci 2019. [DOI: 10.1177/2168479019836979] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
| | - J. Bell
- Elderbrook Solutions GmbH, High Wycombe, United Kingdom
| | - G. Liu
- Merck Research Laboratories, North Wales, PA, USA
| | | | | | | | | | - L. Xu
- Vertex Pharmaceuticals, Boston, MA, USA
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22
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Abstract
The proposed addendum to the International Conference on Harmonization document, Statistical Principles for Clinical Trials, can be read in two ways. There is a new framework for talking about estimands, but is it about fitting present methods into the framework? Or is it about changing methods? My answer: some of each. Where different methods are needed, there are challenging problems in estimating some desirable estimands, but there may also be desirable estimands that can be estimated easily and robustly.
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Affiliation(s)
- Thomas Permutt
- Office of Biostatistics, Office of Translational Sciences, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA
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23
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Permutt T. Defining Treatment Effects: A Primer for Nonstatisticians. Clin Pharmacol Ther 2018; 105:932-934. [PMID: 30471237 DOI: 10.1002/cpt.1313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/15/2018] [Indexed: 11/10/2022]
Abstract
It would often be of interest to know the effect of a drug compared to control in people who take the drug. However, different people will likely take the drug and the control. Thus, comparing takers of the drug to takers of the control does not yield a drug effect. Drug effects in drug takers can be estimated, but first they must be carefully defined.
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Affiliation(s)
- Thomas Permutt
- Office of Biostatistics, Office of Translational Sciences, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, USA
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Roger JH, Bratton DJ, Mayer B, Abellan JJ, Keene ON. Treatment policy estimands for recurrent event data using data collected after cessation of randomised treatment. Pharm Stat 2018; 18:85-95. [DOI: 10.1002/pst.1910] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/16/2018] [Accepted: 09/22/2018] [Indexed: 11/08/2022]
Affiliation(s)
- James H. Roger
- Medical Statistics Department; London School of Hygiene & Tropical Medicine; London UK
| | | | - Bhabita Mayer
- GlaxoSmithKline Research and Development; Middlesex UK
| | - Juan J. Abellan
- GlaxoSmithKline Research and Development; Stevenage Herts UK
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25
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Keene ON. Strategies for composite estimands in confirmatory clinical trials: Examples from trials in nasal polyps and steroid reduction. Pharm Stat 2018; 18:78-84. [PMID: 30370691 DOI: 10.1002/pst.1909] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 08/21/2018] [Accepted: 09/22/2018] [Indexed: 11/11/2022]
Abstract
The draft addendum to the ICH E9 regulatory guideline asks for explicit definition of the treatment effect to be estimated in clinical trials. The draft guideline also introduces the concept of intercurrent events to describe events that occur post-randomisation that may affect efficacy assessment. Composite estimands allow incorporation of intercurrent events in the definition of the endpoint. A common example of an intercurrent event is discontinuation of randomised treatment and use of a composite strategy would assess treatment effect based on a variable that combines the outcome variable of interest with discontinuation of randomised treatment. Use of a composite estimand may avoid the need for imputation which would be required by a treatment policy estimand. The draft guideline gives the example of a binary approach for specifying a composite estimand. When the variable is measured on a non-binary scale, other options are available where the intercurrent event is given an extreme unfavourable value, for example comparison of median values or analysis based on categories of response. This paper reviews approaches to deriving a composite estimand and contrasts the use of this estimand to the treatment policy estimand. The benefits of using each strategy are discussed and examples of the use of the different approaches are given for a clinical trial in nasal polyposis and a steroid reduction trial in severe asthma.
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Wang MD, Liu J, Molenberghs G, Mallinckrodt C. An evaluation of the trimmed mean approach in clinical trials with dropout. Pharm Stat 2018; 17:278-289. [DOI: 10.1002/pst.1858] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 12/15/2017] [Accepted: 02/20/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Ming-Dauh Wang
- Lilly Research Labs; Eli Lilly and Co; Indianapolis IN USA
| | | | - Geert Molenberghs
- I-BioStat; Hasselt University; Diepenbeek Belgium
- I-BioStat; Katholieke Universiteit; Leuven Belgium
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27
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Permutt T. Author's reply to comments on "A taxonomy of estimands for regulatory clinical trials with discontinuations". Stat Med 2017; 36:4417. [PMID: 29110369 DOI: 10.1002/sim.7490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 08/21/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Thomas Permutt
- Center for Drug Evaluation and Research, Office of Biostatistics, Division of Biometrics II, Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland, 20993-0002, USA
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Mehrotra DV, Liu F, Permutt T. Missing data in clinical trials: control-based mean imputation and sensitivity analysis. Pharm Stat 2017. [DOI: 10.1002/pst.1817] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | - Fang Liu
- Clinical Biostatistics; Merck & Co., Inc.; North Wales PA USA
| | - Thomas Permutt
- Office of Biostatistics; Center for Drug Evaluation and Research, FDA; Silver Spring MD USA
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29
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Rosenkranz G. Estimands-new statistical principle or the emperor's new clothes? Pharm Stat 2016; 16:4-5. [PMID: 27966259 DOI: 10.1002/pst.1792] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Gerd Rosenkranz
- Center for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria
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Permutt T. Comments on ‘Estimands in clinical trials - broadening the perspective’. Stat Med 2016; 36:20-21. [DOI: 10.1002/sim.7160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 10/09/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Thomas Permutt
- Division of Biometrics II, Office of Biostatistics, Office of Translational Sciences; Center for Drug Evaluation and Research, U.S. Food and Drug Administration; Maryland U.S.A
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