Adaptive treatment assignment methods and clinical trials.

This paper provides a general review of adaptive experimental designs which utilize accumulating information for assigning the best treatment to the most patients in clinical trials. The historical development of such methods is traced. Though the statistical literture on adaptive designs has developed rapidly and continues to grow, the methods are almost totally unused in practice. An extensive evaluation of why adaptive designs are rarely used in clinical trials is presented. It is asserted that most published methods have important deficiencies that render them unsuitable for application. Suggestions are offered for reorienting this area of research into directions that are potentially more useful for clinical trials.