BOP2-FE: Bayesian optimal phase II design with futility and efficacy-stopping boundaries

The primary purpose of an oncology single-arm trial is to evaluate the effectiveness of anticancer agents and make a go/no-go decision while maintaining patient safety. We propose a flexible Bayesian optimal phase II design with futility and efficacy stopping boundaries for single-arm clinical trials, named the BOP2-FE design. The proposed BOP2-FE design allows for early stopping of efficacy when the observed antitumor effect is sufficiently higher than the null hypothesis value in the interim looks and retains the benefits of the original BOP2 design, such as explicitly controlling the type I error rate while maximizing power, accommodating different types of endpoint, flexible number of interim looks, and stopping boundaries calculated before the start of the trial. Simulation studies show that the BOP2-FE design reduces the total sample size under the alternative hypothesis while strictly controlling the type I error rate and providing a similar statistical power to the original BOP2 design and a higher statistical power than another existing design.