ABSTRACT
The use of adaptive design methods in clinical trials may allow researchers to correct assumptions made at the planning stage and select the most promising option early. In practice, a two-stage seamless adaptive design typically consists of two stages: a learning (or exploratory) phase and a confirmatory phase. The chapter considers the method of sum of p-values (MSP) and apply the general framework to the two-stage design as outlined in Chang and Chow and Chang, which are suitable for the following adaptive designs that allow early efficacy stopping, early stopping for both efficacy and futility, and early futility stopping. Tsiatis and Mehta showed that there exists a more powerful group sequential design for any adaptive design with sample size adjustment. Conditional power with or without clinical trial simulation is often considered for sample size reestimation in adaptive trial designs.
