An Adaptive Timeline Determination of Survival Trials

Adaptive design of survival trials often faces a dilemma. If the target is to use all the event information in the final analysis, there is a limitation on the interim information that may be used for the adaptations. If one wants to use all the interim information for a better stage 2 design, some event information may need to be discarded in the final analysis to properly control Type I error. This article proposes an adaptive design method to bridge this gap. This method allows the use of all the interim information for stage 2 design and the use of all the event information in the final analysis. We prove that a sufficient condition for proper Type I error control for this method is that the final analysis time, potentially depending on all the interim data, converges to some fixed point. We illustrate that such condition is valid in many applications. Because the proposed method uses all the event information, it is more powerful than the existing methods that sacrifice some event information to control the error rate. Simulation study shows our method performs satisfactorily.