An urn based covariate adjusted response adaptive allocation design

A class of Covariate-Adjusted Response-Adaptive Allocation Designs for Multitreatment Binary Response Trials

A class of covariate-adjusted response-adaptive randomization procedures is developed for binary treatment outcomes in a phase III clinical trial set up involving multiple treatments. The target allocation is developed by combining the ethical aspects with statistical precision under the existence of treatment covariate interaction. Relevant measures of the performance for the proposed allocation designs are studied and compared.

Can response-adaptive randomization increase participation in acute stroke trials?

BACKGROUND AND PURPOSE

A response-adaptive randomization (RAR) trial design actively adjusts the ratio of participants assigned to each trial arm, favoring the better performing treatment by using outcome data from participants already in the trial. Compared with a standard clinical trial, an RAR study design has the potential to improve patient participation in acute stroke trials.

METHODS

This cross-sectional randomized survey included adult emergency department patients, age≥18, without symptoms of stroke or other critical illness. A standardized protocol was used, and subjects were randomized to either an RAR or standard hypothetical acute stroke trial. After viewing the video describing the hypothetical trial (http://youtu.be/cKIWduCaPZc), reviewing the consent form, and having questions answered, subjects indicated whether they would consent to the trial. A multivariable logistic regression model was fitted to estimate the impact of RAR while controlling for demographic factors and patient understanding of the design.

RESULTS

A total of 418 subjects (210 standard and 208 RAR) were enrolled. All baseline characteristics were balanced between groups. There was significantly higher participation in the RAR trial (67.3%) versus the standard trial (54.5%), absolute increase: 12.8% (95% confidence interval, 3.7-22.2). The RAR group had a higher odds ratio of agreeing to research (odds ratio, 1.89; 95% confidence interval, 1.2-2.9) while adjusting for patient level factors. Trial designs were generally well understood by the participants.

CONCLUSIONS

The hypothetical RAR trial attracted more research participation than standard randomization. RAR has the potential to increase recruitment and offer benefit to future trial participants.

Managing competing demands in the implementation of response-adaptive randomization in a large multicenter phase III acute stroke trial

It is well known that competing demands exist between the control of important covariate imbalance and protection of treatment allocation randomness in confirmative clinical trials. When implementing a response-adaptive randomization algorithm in confirmative clinical trials designed under a frequentist framework, additional competing demands emerge between the shift of the treatment allocation ratio and the preservation of the power. Based on a large multicenter phase III stroke trial, we present a patient randomization scheme that manages these competing demands by applying a newly developed minimal sufficient balancing design for baseline covariates and a cap on the treatment allocation ratio shift in order to protect the allocation randomness and the power. Statistical properties of this randomization plan are studied by computer simulation. Trial operation characteristics, such as patient enrollment rate and primary outcome response delay, are also incorporated into the randomization plan.

On a class of optimal covariate-adjusted response adaptive designs for survival outcomes

A class of optimal covariate-adjusted response adaptive procedures is developed for phase III clinical trials when the treatment response is a survival time and there is random censoring. The basic aim is to develop an allocation design by combining the ethical aspects with statistical precision in a reasonable way under the presence of covariate information. Considering minimisation of total hazards as the ethical requirement, the proposed procedure is assessed in terms of the assignment to the better treatment and the efficiency (i.e. power) to detect a small departure in treatment effectiveness. The applicability of the proposed methodology is also illustrated using a real data set.

Response-adaptive designs for continuous treatment responses in phase III clinical trials: A review

A variety of response-adaptive randomization procedures have been proposed in literature assuming binary outcomes. However, the list is not so long for continuous outcomes though many real clinical trials deal with continuous treatment responses. In this paper, we attempt to explore the available procedures together with a comparison of their performances. Some real-life adaptive trial is also reviewed.