Table 1.

Types of adaptive trials

Types of adaptive design	Description	Objective of design
Dose finding	Data is reported and extracted in interim reports in as short a time as possible, if technology allows this can be done in close to real time. The data is reviewed as it accumulates and then decisions can be taken and implemented on lowering or raising doses as determined in protocol. It is adaptive as there will not have been a set point where the dose is changed; the design is purposefully flexible and adaptive.	To avoid giving therapeutic doses, or to overdose.
Response adapting	Safety and efficacy data are captured as near to live as possible and further participants are randomized according to outcome of earlier participants. Some have called this a “play-the-winner” approach as subsequent participants are assigned to the treatment arm that has the best efficacy or fewer side effects.	To reduce exposure to an ineffective arm or to side effects.
Amending sample size	Sample sizes are based on assumptions and often there is too little information available that allow for accurate assumptions to be made.7 Therefore, many protocols set a sample size that may be too high or too small. The former results in a trial that exposes participants needless once the question has been answered and the latter results in the trial being unable to answer the question. In an adaptive design the limitation on the power calculations are acknowledged and as the trial begins to inform that assumption so the power calculation can be amended.	Allow the trial to run until the question has been answered and to avoid exposing participants to an experimental therapy unnecessarily.