title: CP function: an alpha spending function based on conditional power.
abstract: Alpha spending function and stochastic curtailment are two frequently used methods in group sequential design. In the stochastic curtailment approach, the actual type I error probability cannot be well controlled within the specified significance level. But conditional power (CP) in stochastic curtailment is easier to be accepted and understood by clinicians. In this paper, we develop a spending function based on the concept of conditional power, named CP function, which combines desirable features of alpha spending and stochastic curtailment. Like other two-parameter functions, CP function is flexible to fit the needs of the trial. A simulation study is conducted to explore the choice of CP boundary in CP function that maximizes the trial power. It is equivalent to, even better than, classical Pocock, O'Brien-Fleming, and quadratic spending function as long as a proper ρ0 is given, which is pre-specified CP threshold for efficacy. It also well controls the overall type I error type I error rate and overcomes the disadvantage of stochastic curtailment.
authors.affiliation: Department of Health Statistics, School of Preventive Medicine, Fourth Military Medical University, Xi'an, Shaanxi, China; Biostatistics and Research Decision Science, Merck Research Laboratory, Merck & Co., Inc., Beijing, China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Jiang
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.forename: Chanjuan
authors.initials: C
authors.lastname: Li
authors.forename: Jielai
authors.initials: J
authors.lastname: Xia
authors.forename: William
authors.initials: W
authors.lastname: Wang
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D002986:Clinical Trials as Topic / Q000379:methods*; D015179:Colorectal Neoplasms / Q000188:drug therapy; D003198:Computer Simulation; D006801:Humans; D015233:Models, Statistical; D009010:Monte Carlo Method; D012107:Research Design
chemical_list: D000970:Antineoplastic Agents
keywords: alpha spending function; conditional power; group sequential design; stochastic curtailment; type I error rate