An overview of methodological considerations regarding adaptive stopping, arm dropping, and randomization in clinical trials

Adaptive features may increase flexibility and efficiency of clinical trials, and improve participants’ chances of being allocated to better interventions. Our objective is to provide thorough guidance on key methodological considerations for adaptive clinical trials. We provide an overview of key methodological considerations for clinical trials employing adaptive stopping, adaptive arm dropping, and response-adaptive randomization. We cover pros and cons of different decisions and provide guidance on using simulation to compare different adaptive trial designs. We focus on Bayesian multi-arm adaptive trials, although the same general considerations apply to frequentist adaptive trials. We provide guidance on 1) interventions and possible common control, 2) outcome selection, follow-up duration and model choice, 3) timing of adaptive analyses, 4) decision rules for adaptive stopping and arm dropping, 5) randomization strategies, 6) performance metrics, their prioritization, and arm selection strategies, and 7) simulations, assessment of performance under different scenarios, and reporting. Finally, we provide an example using a newly developed R simulation engine that may be used to evaluate and compare different adaptive trial designs. This overview may help trialists design better and more transparent adaptive clinical trials and to adequately compare them before initiation. •Adaptive clinical trials are flexible and adaptive features may increase trial efficiency and individual participants' chances of being allocated to superior interventions.•Adaptive trials come with increased complexity and not all adaptive features may always be beneficial.•We provide an overview of and guidance on key methodological considerations for clinical trials employing adaptive stopping, adaptive arm dropping, or response-adaptive randomization.•Further, we provide a simulation engine and example on how to compare adaptive trial designs using simulation.•This guidance paper may help trialists design and plan adaptive clinical trials.