ABSTRACT
Monitoring of accumulating information on efficacy and toxicity data in a clinical trial is an important aspect of human subjects protection. The primary goal of monitoring a clinical trial is to protect patients while allowing sufficient information to be accumulated so that the study objectives can be addressed. Addressing study objectives may include stopping a trial as soon as there is sufficient evidence to demonstrate efficacy, harm, or even lack of benefit. The standards for these objectives may well depend on the disease setting, type of treatment, or other factors (Freidlin and Korn 2009). The objective of an interim monitoring plan is define pre-specified stopping rules that define when a study will be analyzed and under what conditions the trial will be stopped early, while controlling for the study design properties. A well-designed trial is the one in which the analyst has investigated and understands the properties of the trial design. In particular, it is important to have an understanding of when a trial may be stopped either for evidence of activity or for lack of benefit or harm.
