Abstract: The group sequential design is a good choice of oncology trial design because of the smaller sample size and the probability of early stopping for efficacy/futility. To design and apply the group sequential trials scientifically, we illustrate how to choose the number, timing of interim analysis, alpha spending function and optimal trial parameters by employing Monte Carlo simulation. The simulation results show that the three-stage design of 2∶1∶1 time point, whose expected sample size is 420.53, is the best choice in the group sequential design. And the expect sample size is only 420.53. Among the five α spending functions proposed by Lan and DeMets, the 1.5th power and quadratic α spending function, which have the smallest expect sample size of 393 cases, are better than O'Brien-Fleming and Pocock design.

Key words: Oncology clinical trial, Group sequential design, Interim analysis, Sample size estimation