Stopping rules for phase II studies

This paper, the second in a series of three papers concerned with the stati stical aspects of interim analyses in clinical trials, is concerned with st opping rules in phase II clinical trials. Phase II trials are generally sma ll-scale studies, and may include one or more experimental treatments with or without a control. A common feature is that the results primarily determ ine the course of further clinical evaluation of a treatment rather than pr oviding definitive evidence of treatment efficacy. This means that there is more flexibility available in the design and analysis of such studies than in phase III trials. This has led to a range of different approaches bring taken to the statistical design of stopping rules for such trials. This pa per briefly describes and compares the different approaches. In most cases the stopping rules can be described and implemented easily without knowledg e of the detailed statistical and computational methods used to obtain the rules.