Kim Bolland

Mid-trial design reviews for sequential clinical trials

When sequential clinical trials are conducted by plotting a statistic measuring treatment difference against another measuring information, power is guaranteed regardless of nuisance parameters. However, values need to be assigned to nuisance parameters in order to gain an impression of the sample size distribution. Each interim analysis provides an opportunity to re-evaluate the relationship between sample size and information. In this paper we discuss such mid-trial design reviews. In the special cases of trials with a relatively short recruitment phase followed by a longer period of follow-up, and of normally distributed responses, mid-trial design reviews are particularly important. Examples are given of the various situations considered, and extensive simulations are reported demonstrating the validity of the review procedure in the case of normally distributed responses.

Sample size review in a head injury trial with ordered categorical responses

Between 1993 and 1996, a total of 452 patients were entered into a randomized trial evaluating eliprodil (a non-competitive NMDA receptor antagonist) in patients suffering from severe head injury. The primary efficacy analysis concerned the Glasgow Outcome Score (GOS), six months after randomization. This outcome was classified into three ordered categories: good recovery; moderate disability, and the worst category made up by combining severe disability, vegetative state and dead. A sample size calculation was performed prior to the commencement of the study, using a formula which depends on the anticipated proportions of patients in the three different outcome categories, the proportional odds assumption and on the relationship between outcome and prognostic factors such as Glasgow Coma Score at entry. Owing to uncertainty about the influence of prognostic factors, and about the proportion of patients in the three GOS categories, a blinded sample size review was planned. This review was performed on the basis of the first 93 patients to respond, and this led to an increase in the sample size from 400 to 450. In this paper the pre-trial simulations showing that the type I error rate would not be influenced and the power would be preserved will be presented, and the implementation of the procedure will be described.

Formal approaches to safety monitoring of clinical trials in life-threatening conditions.

Large clinical trials in life-threatening conditions are usually conducted under the surveillance of a Data and Safety Monitoring Board (DSMB), whose remit is to protect the ethical and safety interests of the patients. The purpose of this paper is to describe a formal approach to safety monitoring, using a sequential safety procedure to aid the decisions made by the DSMB. This procedure is designed to recommend termination of the study as soon as evidence that the experimental treatment is worse than the control in terms of the primary safety response is so strong that it is unethical to proceed. The use of this formal sequential procedure enables probabilities of the study stopping erroneously and stopping correctly, under various degrees of experimental treatment disadvantage, to be examined. Also scenarios depicting data sets which lead to continuing or stopping can be presented. Such explorations are useful in encouraging all DSMB members to consider carefully, prior to the start of a study, the conditions under which they would seriously wish to consider termination. The implementation of these methods is described for three recently completed trials in which it has been used. Finally, our current recommendations for the design of these procedures, arising from these and other similar experiences, are given.

Evaluation of a sequential global test of improved recovery following stroke as applied to the ICTUS trial of citicoline.

The International Citicoline Trial in acUte Stroke is a sequential phase III study of the use of the drug citicoline in the treatment of acute ischaemic stroke, which was initiated in 2006 in 56 treatment centres. The primary objective of the trial is to demonstrate improved recovery of patients randomized to citicoline relative to those randomized to placebo after 12 weeks of follow-up. The primary analysis will take the form of a global test combining the dichotomized results of assessments on three well-established scales: the Barthel Index, the modified Rankin scale and the National Institutes of Health Stroke Scale. This approach was previously used in the analysis of the influential National Institute of Neurological Disorders and Stroke trial of recombinant tissue plasminogen activator in stroke.The purpose of this paper is to describe how this trial was designed, and in particular how the simultaneous objectives of taking into account three assessment scales, performing a series of interim analyses and conducting treatment allocation and adjusting the analyses to account for prognostic factors, including more than 50 treatment centres, were addressed.

Using Historical Lesion Volume Data in the Design of a New Phase II Clinical Trial in Acute Stroke

Background and Purpose— Clinical research into the treatment of acute stroke is complicated, is costly, and has often been unsuccessful. Developments in imaging technology based on computed tomography and magnetic resonance imaging scans offer opportunities for screening experimental therapies during phase II testing so as to deliver only the most promising interventions to phase III. We discuss the design and the appropriate sample size for phase II studies in stroke based on lesion volume. Methods— Determination of the relation between analyses of lesion volumes and of neurologic outcomes is illustrated using data from placebo trial patients from the Virtual International Stroke Trials Archive. The size of an effect on lesion volume that would lead to a clinically relevant treatment effect in terms of a measure, such as modified Rankin score (mRS), is found. The sample size to detect that magnitude of effect on lesion volume is then calculated. Simulation is used to evaluate different criteria for proceeding from phase II to phase III. Results— The odds ratios for mRS correspond roughly to the square root of odds ratios for lesion volume, implying that for equivalent power specifications, sample sizes based on lesion volumes should be about one fourth of those based on mRS. Relaxation of power requirements, appropriate for phase II, lead to further sample size reductions. For example, a phase III trial comparing a novel treatment with placebo with a total sample size of 1518 patients might be motivated from a phase II trial of 126 patients comparing the same 2 treatment arms. Discussion— Definitive phase III trials in stroke should aim to demonstrate significant effects of treatment on clinical outcomes. However, more direct outcomes such as lesion volume can be useful in phase II for determining whether such phase III trials should be undertaken in the first place.

How a Sequential Design Would Have Affected the GAIN International Study of Gavestinel in Stroke

While planning the GAIN International Study of gavestinel in acute stroke, a sequential triangular test was proposed but not implemented. Before the trial commenced it was agreed to evaluate the sequential design retrospectively to evaluate the differences in the resulting analyses, trial durations and sample sizes in order to assess the potential of sequential procedures for future stroke trials. This paper presents four sequential reconstructions of the GAIN study made under various scenarios. For the data as observed, the sequential design would have reduced the trial sample size by 234 patients and shortened its duration by 3 or 4 months. Had the study not achieved a recruitment rate that far exceeded expectation, the advantages of the sequential design would have been much greater. Sequential designs appear to be an attractive option for trials in stroke.

A safety monitoring procedure for a clinical drug development program, with application to the assessment of a novel COX-2 inhibitor.

Formal safety monitoring procedures are well-developed for use in individual clinical trials and provide valuable guidance to Independent Data Monitoring Committees (IDMCs). Less has been written about procedures for use over the whole of a drug development program. It is becoming common for a single IDMC to be appointed for a whole series of studies involving a single compound. While each study will have its own goals in terms of efficacy, safety, or both, there is the potential for all of them to contribute to an emerging picture of safety. Indeed, an IDMC overseeing several studies will need to integrate the data coming from each and a formal pre-defined approach can be a valuable aid. Formal procedures are especially relevant in situations where one or two undesirable events are recognized from the outset as being of particular concern. In some cases this might be death, and in the example discussed here it is a cardiovascular event of the type that has been found to be related to certain COX-2 inhibitors. In this paper a design proposal for a safety monitoring procedure for use by an IDMC during the development of a new COX-2 inhibitor will be described.

54 The use of a sample size review in a head injury trial with ordered categorical responses

Between 1993 and 1996, a total of 452 patients were entered into a randomized trial evaluating eliprodil (a non-competitive NMDA receptor antagonist) in patients suffering from severe head injury. The primary efficacy analysis concerned the Glasgow Outcome Score (GOS), six months after randomization. This outcome was classified into three ordered categories: good recovery; moderate disability, and the worst category made up by combining severe disability, vegetative state and dead. A sample size calculation was performed prior to the commencement of the study, using a formula which depends on the anticipated proportions of patients in the three different outcome categories, the proportional odds assumption and on the relationship between outcome and prognostic factors such as Glasgow Coma Score at entry. Owing to uncertainty about the influence of prognostic factors, and about the proportion of patients in the three GOS categories, a blinded sample size review was planned. This review was performed on the basis of the first 93 patients to respond, and this led to an increase in the sample size from 400 to 450. In this paper the pre-trial simulations showing that the type I error rate would be influenced and the power would be preserved will be presented, and the implementation of the procedure will be described.