Terminating a trial -- the ethical problem

Clinical trials of medical devices and implants: ethical concerns

Various ethical concerns that are essential elements in the critical trial of any new treatment modality are examined. Problems surrounding the issue of informed consent are considered. Conflicts between therapeutic and research considerations are discussed. The role of double-blind studies is examined.

Planning of clinical trials

This article focuses on steps of planning clinical trials most relevant to the question the clinician asks and how this question is properly transformed in a design and a protocol. All steps are important for the data quality or the validity of the results. A clinical trial is an experiment aimed at testing an hypothesis regarding the efficacy of a given intervention on an event, symptom or impaired quality of life in patients with a defined condition and a particular profile. As such, it should meet the fundamentals of scientific discovery that guarantee causality between the observed difference and the intervention. All the planning components are thought according to these fundamentals.

When are placebo-controlled trials no longer appropriate?

This paper presents a standard for assessing the validity of placebo-controlled trials in circumstances in which such trials might be unjustly denying appropriate therapies to members of the control group. This standard categorizes the types of risks that can or cannot be imposed upon consenting research subjects in such control groups. The paper also shows how needed research can be conducted while respecting the proposed ethical standard. Both the problem and the proposed standard are illustrated by reference to the major trials of the thrombolytic agents.

Surgical procedures and devices should be evaluated in the same way as medical therapy

This paper is a personal essay that starts and ends with the message that surgical procedures and devices should be evaluated in the same way as medical therapies, namely, by randomized clinical trials (RCTs). I discuss, with particular attention to surgical procedures and devices, the objections raised against RCTs in medical decision-making, a schema for utilizing the traditional phases of RCTs in the evaluation of surgical procedures and devices, the importance of RCTs to FDA approval, financial compensation, and health care costs, the impact of RCTs on clinical practice, the role of RCTs in academia, teaching, and research, and the surgeon's obligation to participate in a leadership role in RCTs. The belief is expressed that national funding of health care should mandate allocations for RCTs and that such expenditures, as well as the spending of health care dollars on the basis of the outcomes of such trials, will not only improve patient management in the shortest time but will eventually reduce health care costs. The RCT, by selecting effective and safe surgical procedures and devices, as well as diets and drugs, is the best means science has to assess the validity of patient management.

The early termination of clinical trials: causes, consequences, and control. With special reference to trials in the field of arrhythmias and sudden death. Task Force of the Working Group on Arrhythmias of the European Society of Cardiology

The early termination of clinical trials, for either benefit or harm, often generates undue enthusiasm or alarm. The enhanced publicity attending early termination of a trial promotes inappropriate interpretations that are favored by the inherent difficulty of prompt and comprehensive data review. Furthermore, the process of monitoring the accumulating outcome data for early evidence of treatment benefit or harm is fraught with many statistical and methodological difficulties. This report from a task force convened by the Working Group on Arrhythmias of the European Society of Cardiology incorporates first, a series of trials terminated appropriately or inappropriately for benefit or harm and used as examples to illustrate the importance of suitable trial design and of proper stopping rules; second, a description of the committee structure of a clinical trial; third, an analysis of the general design issues; fourth, a review of the main issues in interim analysis with special reference to main strategies for reducing the rate of false-positive claims that could result from early trial termination; and finally, a series of specific recommendations concerning the design, structure, analysis, interpretation, and presentation of a clinical trial.

Exact repeated confidence intervals for Bernoulli parameters in a group sequential clinical trial

This paper presents methods for constructing exact repeated confidence intervals (RCIs) for the success probability, p, of a single Bernoulli treatment and for the difference of success probabilities, delta = p1-p2, of two independent Bernoulli treatments in the context of a group sequential clinical trial. These RCIs calculated at each interim analysis are useful for evaluating the data in light of all the information available rather than relying on rigid stopping criteria used by repeated significance tests. Extensions to construction of RCIs for the relative risk p = p1/p2 and odds ratio psi = p1(1-p2)/p2(1-p1) are indicated.

Operational and policy considerations of data monitoring in clinical trials: the Diabetes Control and Complications Trial experience

Many clinical trials incorporate a system for monitoring emerging data that utilizes a committee composed of individuals who are independent of the investigators conducting the study. Although this is a common practice, there is a paucity of publications examining the operating methods of these groups. This paper describes the composition, functions, and procedures of the Data, Safety and Quality Review Group (DSQ) of the Diabetes Control and Complications Trial (DCCT). The DSQ is not masked to emerging data and the voting membership is made up of individuals with a wide diversity of expertise that reflects the needs of the trial. There are also nonvoting exofficio members who represent other components of the study organization. In addition to data monitoring, the DSQ provides external review of coordinating center operations. A distinctive aspect of the DCCT's DSQ is the creation of a free-standing operations manual for the DSQ's use during the trial and the involvement of the study investigators in developing certain sections of this document. Utilizing a process that allowed participation of the investigators was considered critical to achieving a mutual understanding regarding the planned uses and interpretations of the study data prior to the study's completion so as to minimize the chances of major disagreements regarding the conclusions drawn. Equally important, the existence of such a manual provides documentable reassurance to all interested parties that both scientific integrity and patient safety are being closely watched and gives the study investigators confidence that the results of the study will be scientifically credible and clinically important.

Monitoring versus interim analysis of clinical trials: a perspective from the pharmaceutical industry

The definitions of "interim analysis" and "monitoring" of clinical trials are often ambiguous in the current literature. The resulting confusion can lead to erroneous conclusions and misguided decisions, especially when activities that are operational or observational are evaluated in a probabilistic sense as inferential. The authors seek to define "interim analysis" and "monitoring" in a mutually exclusive fashion. These definitions will then provide the opportunity to review and categorize existing clinical trial practices and procedures. This will clarify such issues as "when to look" and "when to pay a price" (e.g., test size and power) and characterize such issues in the context of pharmaceutical industry drug development.

Equipoise and the ethics of clinical research

The ethics of clinical research requires equipoise--a state of genuine uncertainty on the part of the clinical investigator regarding the comparative therapeutic merits of each arm in a trial. Should the investigator discover that one treatment is of superior therapeutic merit, he or she is ethically obliged to offer that treatment. The current understanding of this requirement, which entails that the investigator have no "treatment preference" throughout the course of the trial, presents nearly insuperable obstacles to the ethical commencement or completion of a controlled trial and may also contribute to the termination of trials because of the failure to enroll enough patients. I suggest an alternative concept of equipoise, which would be based on present or imminent controversy in the clinical community over the preferred treatment. According to this concept of "clinical equipoise," the requirement is satisfied if there is genuine uncertainty within the expert medical community--not necessarily on the part of the individual investigator--about the preferred treatment.

Review: clinical trials in peptic ulcer disease--problems of methodology and interpretation

This review focuses on the methodology and interpretation of drug trials in peptic ulcer disease. The problems of planning and conduct that are discussed include the ethics of using placebo, eligibility criteria, estimations of sample size, stopping rules, randomization, blinding, and efficacy criteria, that is, ulcer healing and pain relief in the short term and prevention of relapse and complications in the long term. Statistical topics covered include confidence intervals, evaluation of survival type data, post-stratification, and sub-group analysis. The difference between clinical and statistical significance is discussed, major problems being overemphasis on P-value, type II errors, and post hoc power determinations. Explanatory and pragmatic questions are based on compliance-to-protocol and intention-to-treat cohorts, respectively, and involve problems of compliance testing, evaluation of withdrawals, and the use of fixed-dose regimens. The rather slow process for clinical trials to gain acceptance is described, and it is proposed to rely on disease-related and behavioural barriers, lack of knowledge of the inherent limitations of methodology, and overemphasis on the subject of peptic ulcer healing, in addition to some concern at the relevance of assessing long-term drug intervention by repeated endoscopies rather than by studying symptoms and the incidence of complications. We foresee an increased impact of clinical trials on ulcer research and therapeutic decision making, provided physicians are able to develop the proper methodology to answer the relevant questions.

A predictive approach to selecting the size of a clinical trial, based on subjective clinical opinion

The 'textbook' approach to determining sample size in a clinical trial has some fundamental weaknesses which we discuss. We describe a new predictive method which takes account of prior clinical opinion about the treatment difference. The method adopts the point of clinical equivalence (determined by interviewing the clinical participants) as the null hypothesis. Decision rules at the end of the study are based on whether the interval estimate of the treatment difference (classical or Bayesian) includes the null hypothesis. The prior distribution is used to predict the probabilities of making the decisions to use one or other treatment or to reserve final judgement. It is recommended that sample size be chosen to control the predicted probability of the last of these decisions. An example is given from a multi-centre trial of superficial bladder cancer.

Loss weighting and the human cost of experimentation

This paper analyzes the dilemma faced by clinicians who must determine a proper sample size for a clinical trial. A large sample size may be used to ensure significant results. In so doing, many patients may be randomized to the wrong arm of a clinical trial. Alternatively, fewer patients may be used in a clinical trial, however, the resulting conclusions will be less certain, and future patients may be harmed by false conclusions. This study introduces a ratio of relative human cost or loss associated with a single present patient receiving incorrect therapy during the clinical trial to a single future patient given incorrect therapy after the trial is over. This "loss weighting" ratio can be estimated, the trade-off between present and future loss can be evaluated and the total loss from a clinical trial can be minimized. The resulting method, based on the loss weighting ratio, suggests an inverse relationship between the number of future patients potentially affected by a clinical trial and the size of desired type I and type II error. The conclusions derived from this paper can be incorporated easily into the current process of sample size determination. This is illustrated with examples from two well-known clinical trials.

Assessing possible late treatment effects in stopping a clinical trial early: a case study. Diabetic Retinopathy Study report No. 9

Suppose a fixed-sample trial in a disease with a long response time shows a statistically significant benefit of the experimental treatment before patients have completed the planned follow-up period. The question may then arise--and did arise in the Diabetic Retinopathy Study (DRS)--whether the observed early benefit of treatment may be offset at some time in the future by the subsequent development of harmful treatment effects. If this question raises serious concerns, then the investigators are faced with a dilemma. If the trial is stopped because of the observed early treatment benefit and the treatment is administered to the untreated control group as well as to patients outside the study, and if the treatment is later found to have deleterious effects, then it may ultimately do more harm than good to patients. Moreover, the fact that the treatment is harmful may never become known. If, on the other hand, the trial is not stopped and the treatment proves to have no deleterious effects, then the control group and patients outside the study would be harmed because the treatment was withheld. We show how, in the DRS, this very problem was formulated and resolved. First a severe, delayed harmful treatment effect was postulated. Projections based on this postulation showed that the early gains were so great that they were unlikely to be offset--ever. Based in part on these projections, the following decisions were made: (a) the study protocol would be changed so as to allow treatment of the untreated control group, and (b) patients would continue to be followed in order to make possible the detection of late, harmful treatment effects, should they develop.

Changing the protocol: a case report from the Macular Photocoagulation Study. Macular Photocoagulation Study Group

The first report of findings from the Senile Macular Degeneration Study (SMDS), one of several clinical trials carried out by the Macular Photocoagulation Study (MPS) Group, appeared in June 1982. Although the SMDS did not terminate with the change of protocol that precipitated release of the initial findings of the trial, activities prior to and immediately following the decision to halt recruitment and publish findings were disruptive to the operations of all centers and to the professional and personal lives of the individuals with greatest responsibility for implementing the change. The purpose of this report is to describe the experiences of the MPS investigators in the hope that others may learn from them. The issues that confronted the investigators are discussed. The decisions they made, a chronology of events, and activities leading to the decision to terminate patient enrollment in the SMDS and to release findings from the trial are described.

Repeated confidence intervals for group sequential clinical trials

We describe methods for the construction of valid confidence intervals for parameters of interest at repeated times during the course of a clinical trial with two treatments. This approach gives the investigator a way to monitor the trial and allows greater flexibility than methods that have rigid statistical stopping rules. Two situations are considered. In the first, responses are available immediately and normally distributed, the parameter of interest being the difference in means. In the second, observations are survival times and a proportional hazards model is assumed. Here the parameter of interest is the hazard ratio. Group sequential tests can be based on repeated confidence interval methods and these are compared to other multiple testing procedures that have been proposed.

Critical reflections on clinical trials

There is often concern about the large number of patients needed for a particular clinical trial. However, one could be equally concerned that a trial is designed with a number of patients that is too small to obtain a precise enough estimate of the difference between the success rates of the treatments. The design of the trial should ensure that statistical significance is only reached if the treatment difference exceeds a specified value of clinical importance. Designs with this property generally require more than the usual number of patients. It is hoped that discussion on the ethical acceptability of this consequence will be stimulated by this paper.