Approaches to interim analysis of randomized clinical trials in cancer: a survey from the Italian National Monitoring Centre for Clinical Trials

Background: Several important questions have been raised about the decision to stop a randomized trial early and on what basis to reach such a decision, particularly in treatment trials in chronic life-threatening diseases, like cancer. A range of formal statistical approaches can be used as a basis for judging at what point such differences are so extreme as to be sufficiently unlikely to reflect the play of chance. However, although interim analysis approaches in clinical trials are widely known, information on current practice of planned monitoring is still scarce. Reports of studies rarely include details on the strategies for both data monitoring and interim analysis. Objectives: To investigate the forms of monitoring used in cancer clinical trials and in particular to gather information on the role of interim analyses in the data monitoring process of a clinical trial. Methods: This project focused on the prevalence of different types of interim analyses and data monitoring in cancer clinical trials. Source of investigation were the protocols of cancer clinical trials included in the Italian Registry of Clinical Trials from 2000 to 2005 Results: The analysis of the collected protocols reveals that only 70.7% of the protocols incorporate statistical interim analysis plans. Despite the large availability of statistical methods for interim analysis, almost the only approach used is the frequentist method, with O'Brien and Fleming boundaries. Presence of a data and safety monitoring committee is planned in 65.3% of protocols, but information on composition and rules to be implemented is lacking. Overall neither form of monitoring is found in 20.0% of the protocols. Conclusions: The results indicate that there is insufficient attention paid to the practical procedures of interim analysis not only by the researchers, but also by regulatory bodies.