Early stopping in clinical PET studies: How to reduce expense and exposure.

Clinical positron emission tomography (PET) research is costly and entails exposing participants to radioactivity. Researchers should therefore aim to include just the number of subjects needed to fulfill the purpose of the study. In this tutorial we show how to apply sequential Bayes Factor testing in order to stop the recruitment of subjects in a clinical PET study as soon as enough data have been collected to make a conclusion. By using simulations, we demonstrate that it is possible to stop a study early, while keeping the number of erroneous conclusions low. We then apply sequential Bayes Factor testing to a real PET data set and show that it is possible to obtain support in favor of an effect while simultaneously reducing the sample size with 30%. Using this procedure allows researchers to reduce expense and radioactivity exposure for a range of effect sizes relevant for PET research.

Typology of drug discontinuation trials - Methodological recommendations.

OBJECTIVE: Due to the increasing concerns about polypharmacy, there is a growing need for clinical recommendations for drug discontinuation. This requires studies investigating the process on several levels. This paper addresses the methodological problems of drug discontinuation trials (DDTs). To that end, we offer a new typology of research aims and corresponding methodological recommendations for trials evaluating drug discontinuation. STUDY DESIGN AND SETTING: Multi-stage development process, including literature search and expert panels. RESULTS: Clinical trials are only required in cases of scientific uncertainty. We identified three situations of uncertainty associated with drug discontinuation from which we derived three study types: 1) Uncertainty regarding the effectiveness and/or safety of a drug; 2) Uncertainty regarding the procedure of discontinuing a previously taken drug; 3) Uncertainty regarding the effectiveness of complex strategies used to discontinue one or more drugs. We developed specific methodological recommendations for each study type. CONCLUSION: We offer a comprehensive definition of research aims, study designs, and methodological recommendations regarding DDTs. The typology we propose can help investigators clarify their research aims and study design. The type-specific methodological recommendation should improve the quality of future drug discontinuation trials.

Sex, Permanent Drug Discontinuation, and Study Retention in Clinical Trials: Insights From the TIMI trials.

BACKGROUND: Women are underrepresented across cardiovascular clinical trials. Whether women are more likely than men to prematurely discontinue study drug or withdraw consent once enrolled in a clinical trial is unknown. METHODS: Eleven phase 3/4 TIMI (Thrombolysis in Myocardial Infarction) trials were included (135 879 men and 51 812 women [28%]). The association between sex and premature study drug discontinuation and withdrawal of consent were examined by multivariable logistic regression after adjusting for potential confounders in each individual trial and combining the individual point estimates in random effects models. RESULTS: After adjusting for baseline differences, women had 22% higher odds of premature drug discontinuation (adjusted odds ratio [ORadj], 1.22 [95% CI, 1.16-1.28]; P<0.001) compared with men. Qualitatively consistent results were observed for women versus men in the placebo arms (ORadj, 1.20 [95% CI, 1.13-1.27]) and active therapy arms (ORadj, 1.23 [95% CI, 1.17-1.30)]; there was some evidence for regional heterogeneity (P interaction <0.001). Of those who stopped study drug prematurely, a similar proportion of men and women in the active arm stopped because of an adverse event (36% for both; P=0.60). Women were also more likely to withdraw consent compared with men (ORadj, 1.26 [95% CI, 1.17-1.36]; P<0.001). CONCLUSIONS: Women were more likely than men to prematurely discontinue study drug and withdraw consent across cardiovascular outcome trials. Premature study drug discontinuation was not explained by baseline differences by sex or a higher proportion of adverse events. Future trials should better capture reasons for drug discontinuation and withdrawal of consent to understand barriers to continued study drug use and clinical trial participation, particularly among women.

Pride and Prejudice during the COVID-19 Pandemic: The Misfortune of Inappropriate Clinical Trial Design.

Coronavirus Disease 2019 (COVID-19) is a rapidly evolving global pandemic for which more than a thousand clinical trials have been registered to secure therapeutic effectiveness, expeditiously. Most of these are single-center non-randomized studies rather than multi-center, randomized controlled trials. Single-arm trials have several limitations and may be conducted when spontaneous improvement is not anticipated, small placebo effect exists, and randomization to a placebo is not ethical. In an emergency where saving lives takes precedence, it is ethical to conduct trials with any scientifically proven design, however, safety must not be compromised. A phase II or III trial can be conducted directly in a pandemic with appropriate checkpoints and stopping rules. COVID-19 has two management paradigms- antivirals, or treatment of its complications. Simultaneous assessment of two different treatments can be done using 2 × 2 factorial schema. World Health Organization's SOLIDARITY trial is a classic example of the global research protocol which can evaluate the preferred treatment to combat COVID-19 pandemic. Short of that, a trial design must incorporate the practicality of the intervention used, and an appropriate primary endpoint which should ideally be a clinical outcome. Collaboration between institutions is needed more than ever to successfully execute and accrue in randomized trials.

COVID-19 hits a trial: Arguments against hastily deviating from the plan.

The COVID-19 pandemic has substantially impacted the conduct of clinical trials. While initially preparing for a period of time, where it would likely be impossible to supervise trials in the usual way and precautionary measures had to be implemented to care for medication supply and general safety of study participants it is now important to consider, how the impact of the pandemic on trial outcome can be assessed, which measures are needed to decide, how to proceed with the trial and what is needed to compensate to irregularity introduced by the pandemic situation. Obviously not all trials will suffer to the same degree: some trials may be close to finalizing recruitment, others may not yet have started. Similarly not all clinical trials investigate vulnerable patient populations, but some will and may in addition have recruited to an extent that beneficial effects achieved in the initial phase of the trial may be outweighed by an increase e.g. in mortality that impacts both treatment groups. The situation is further complicated by the fact that the pandemic reached different countries in the world and even cities in one country at different points in time with different severity. Our example is a randomized and double-blind clinical trial comparing digitoxin and placebo in patients with advanced chronic heart failure. This trial has recruited roughly 1/3 of the overall 2200 patients when the disease outbreak reached Germany. We discuss how simulations and theoretical considerations can be used to address questions about the need to increase the overall sample-size to be recruited to compensate for a potential shrinkage of the treatment effect caused by the COVID-19 pandemic and what role the degree of consistency could play when comparing pre-, during- and post- COVID-19 periods of trial conduct regarding the question, whether the treatment effect can be considered consistent and with this generalizable. This is dependent on the size of the treatment effect and the impact of the pandemic. We argue, that in case of doubt, it may be wise to proceed with the original study plan.

A two-stage phase II clinical trial design with nested criteria for early stopping and efficacy.

We propose a two-stage design for a single arm clinical trial with an early stopping rule for futility. This design employs different endpoints to assess early stopping and efficacy. The early stopping rule is based on a criteria determined more quickly than that for efficacy. These separate criteria are also nested in the sense that efficacy is a special case of, but usually not identical to, the early stopping endpoint. The design readily allows for planning in terms of statistical significance, power, expected sample size, and expected duration. This method is illustrated with a phase II design comparing rates of disease progression in elderly patients treated for lung cancer to rates found using a historical control. In this example, the early stopping rule is based on the number of patients who exhibit progression-free survival (PFS) at 2 months post treatment follow-up. Efficacy is judged by the number of patients who have PFS at 6 months. We demonstrate our design has expected sample size and power comparable with the Simon two-stage design but exhibits shorter expected duration under a range of useful parameter values.

Comparison of conditional bias-adjusted estimators for interim analysis in clinical trials with survival data.

Group sequential designs are widely used in clinical trials to determine whether a trial should be terminated early. In such trials, maximum likelihood estimates are often used to describe the difference in efficacy between the experimental and reference treatments; however, these are well known for displaying conditional and unconditional biases. Established bias-adjusted estimators include the conditional mean-adjusted estimator (CMAE), conditional median unbiased estimator, conditional uniformly minimum variance unbiased estimator (CUMVUE), and weighted estimator. However, their performances have been inadequately investigated. In this study, we review the characteristics of these bias-adjusted estimators and compare their conditional bias, overall bias, and conditional mean-squared errors in clinical trials with survival endpoints through simulation studies. The coverage probabilities of the confidence intervals for the four estimators are also evaluated. We find that the CMAE reduced conditional bias and showed relatively small conditional mean-squared errors when the trials terminated at the interim analysis. The conditional coverage probability of the conditional median unbiased estimator was well below the nominal value. In trials that did not terminate early, the CUMVUE performed with less bias and an acceptable conditional coverage probability than was observed for the other estimators. In conclusion, when planning an interim analysis, we recommend using the CUMVUE for trials that do not terminate early and the CMAE for those that terminate early. Copyright © 2017 John Wiley & Sons, Ltd.

Quantifying the bias in the estimated treatment effect in randomized trials having interim analyses and a rule for early stopping for futility.

In this paper, we consider the potential bias in the estimated treatment effect obtained from clinical trials, the protocols of which include the possibility of interim analyses and an early termination of the study for reasons of futility. In particular, by considering the conditional power at an interim analysis, we derive analytic expressions for various parameters of interest: (i) the underestimation or overestimation of the treatment effect in studies that stop for futility; (ii) the impact of the interim analyses on the estimation of treatment effect in studies that are completed, i.e. that do not stop for futility; (iii) the overall estimation bias in the estimated treatment effect in a single study with such a stopping rule; and (iv) the probability of stopping at an interim analysis. We evaluate these general expressions numerically for typical trial scenarios. Results show that the parameters of interest depend on a number of factors, including the true underlying treatment effect, the difference that the trial is designed to detect, the study power, the number of planned interim analyses and what assumption is made about future data to be observed after an interim analysis. Because the probability of stopping early is small for many practical situations, the overall bias is often small, but a more serious issue is the potential for substantial underestimation of the treatment effect in studies that actually stop for futility. We also consider these ideas using data from an illustrative trial that did stop for futility at an interim analysis. Copyright © 2017 John Wiley & Sons, Ltd.

Landscape of early clinical trials for childhood and adolescence cancer in Spain

Purpose: Despite numerous advances, survival remains dismal for children and adolescents with poor prognosis cancers or those who relapse or are refractory to first line treatment. There is, therefore, a major unmet need for new drugs. Recent advances in the knowledge of molecular tumor biology open the door to more adapted therapies according to individual alterations. Promising results in the adult anticancer drug development have not yet been translated into clinical practice. We report the activity in early pediatric oncology trials in Spain. Methods: All members of the Spanish Society of Pediatric Hematology Oncology (SEHOP) were contacted to obtain information about early trials open in each center. Results: 22 phase I and II trials were open as of May 2015: 15 for solid tumors (68 %) and 7 for hematological malignancies (32 %). Fourteen (64 %) were industry sponsored. Since 2010, four centers have joined the Innovative Therapies For Children With Cancer, an international consortium whose aim is developing novel therapies for pediatric cancers. A substantial number of studies have opened in these 5 years, improving the portfolio of trials for children. Results of recently closed trials show the contribution of Spanish investigators, the introduction of molecularly targeted agents and their benefits. Conclusions: Clinical trials are the way to evaluate new drugs, avoiding the use of off-label drugs that carry significant risks. The Spanish pediatric oncology community through the SEHOP is committed to develop and participate in collaborative academic trials, to favor the advancement and optimization of existing therapies in pediatric cancer (AU)

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A Pocock approach to sequential meta-analysis of clinical trials.

Three recent papers have provided sequential methods for meta-analysis of two-treatment randomized clinical trials. This paper provides an alternate approach that has three desirable features. First, when carried out prospectively (i.e., we only have the results up to the time of our current analysis), we do not require knowledge of the information fraction (the fraction of the total information that is available at each analysis). Second, the methods work even if the expected values of the effect sizes vary from study to study. Finally, our methods have easily interpretable metrics that make sense under changing effect sizes. Although the other published methods can be adapted to be "group sequential" (recommended), meaning that a set number and timing of looks are specified, rather than looking after every trial, ours can be used in both a continuous or group sequential manner. We provide an example on the role of probiotics in preventing necrotizing enterocolitis in preterm infants.

Influence of adaptive analysis on unnecessary patient recruitment: reanalysis of the RATPAC trial.

STUDY OBJECTIVE: Recruitment to clinical trials is a challenging but essential activity in emergency medicine. Conventional fixed-sample trials may continue to recruit patients after efficacy has been demonstrated or when further recruitment is futile. Adaptive trials make use of emerging information to modify aspects of a trial or terminate it prematurely, potentially resulting in savings in terms of sample size, time, and cost. We aim to use sequential testing procedures to reanalyze data from a fixed-sample trial, the Randomised Assessment of Treatment Using Panel Assay of Cardiac Markers (RATPAC) trial, and investigate the potential for adaptive designs to reduce unnecessary recruitment. METHODS: The trial was reanalyzed with a triangular group sequential design, with interim analyses planned every 3 months. Patients were analyzed in the order in which they entered the original trial. RESULTS: We found that the RATPAC trial could potentially have stopped 1 year earlier, with 722 patients enrolled compared with 2,243 patients in the original trial, making a potential saving of approximately $390,000. Estimates of effect were similar, and the qualitative conclusions of the original and group sequential RATPAC trials were in agreement. However, the group sequential approach is not without limitations and would have resulted in less precise estimates of effect and less information available for the subsequent evaluation of secondary endpoints. CONCLUSION: Sequential designs are well suited in emergency medicine because of the rapidly obtained outcomes and the need to avoid unnecessary recruitment. We recommend that group sequential designs be considered for clinical trials in emergency medicine.

An overview of the adaptive designs accelerating promising trials into treatments (ADAPT-IT) project.

Randomized clinical trials, which aim to determine the efficacy and safety of drugs and medical devices, are a complex enterprise with myriad challenges, stakeholders, and traditions. Although the primary goal is scientific discovery, clinical trials must also fulfill regulatory, clinical, and ethical requirements. Innovations in clinical trials methodology have the potential to improve the quality of knowledge gained from trials, the protection of human subjects, and the efficiency of clinical research. Adaptive clinical trial methods represent a broad category of innovations intended to address a variety of long-standing challenges faced by investigators, such as sensitivity to previous assumptions and delayed identification of ineffective treatments. The implementation of adaptive clinical trial methods, however, requires greater planning and simulation compared with a more traditional design, along with more advanced administrative infrastructure for trial execution. The value of adaptive clinical trial methods in exploratory phase (phase 2) clinical research is generally well accepted, but the potential value and challenges of applying adaptive clinical trial methods in large confirmatory phase clinical trials are relatively unexplored, particularly in the academic setting. In the Adaptive Designs Accelerating Promising Trials Into Treatments (ADAPT-IT) project, a multidisciplinary team is studying how adaptive clinical trial methods could be implemented in planning actual confirmatory phase trials in an established, National Institutes of Health-funded clinical trials network. The overarching objectives of ADAPT-IT are to identify and quantitatively characterize the adaptive clinical trial methods of greatest potential value in confirmatory phase clinical trials and to elicit and understand the enthusiasms and concerns of key stakeholders that influence their willingness to try these innovative strategies.

Early stopping rules in oncology: considerations for clinicians.

The number of cancer-related clinical trials has been rapidly increasing over the past decade. Along with this increase, oncology studies stopped early for benefit or harm have also been more common. Clinicians treating cancer patients often are faced with the challenge of having to decide whether or not to incorporate information from these new studies into their daily clinical practice. This review article explains the role of the Data and Safety Monitoring Committee in stopping trials early; provides examples of oncology trials stopped early; and reviews some of the controversies and statistical concepts associated with early stopping rules. In addition, a simple and practical approach to interpreting the findings of trials that are stopped early is provided to assist clinicians in deciding how to incorporate information from these studies into their daily practice.

Randomised controlled trials in oncology closed early for benefit: trends in methodology, results, and interpretation.

PURPOSE: To assess methodology, results and interpretation of oncology randomised controlled trials closed early for benefit (RCTCEB). METHODS: Structured literature search (1950-2008) to identify all published oncology RCTCEB. We then searched for related follow-up articles and conference abstracts to evaluate whether study results and conclusions changed with longer follow-up. A standardised data abstraction process captured information related to statistical methodology, details of interim analyses, results and conclusions. Original articles and follow-up reports were compared for results of primary end-point and author conclusions. RESULTS: We identified 71 RCTCEB. In 16 articles (23%) the study primary end-point was not explicitly stated. Most trials were open to accrual (47/71, 66%) at the time of closure. Formal interim analysis was performed in 65 (92%) trials of which 72% (47/65) was reported as planned; 82% (53/65) reported stopping rules. Trials on average accrued 75% of the planned sample size. Amongst the 23 (32%) RCTCEB with follow-up reports, in only one case did the study results or conclusions change substantially. CONCLUSIONS: While the majority of oncology RCTCEB follows rigourous methodological principles, an important percentage includes limitations in design and/or analysis. Amongst the 23 studies with subsequent follow-up reports, initial results were confirmed in 22 (96%).