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Although the decision to continue or to stop prematurely a clinical trial is not solely based on statistical tests, they bring useful objective arguments to the data monitoring board. However, the multiple use of statistical tests leads to increase the risk of false positive conclusions in favor of one of the treatments, and several methods have been developed to address this problem. This article presents the four major strategies that are being used for monitoring clinical trials, as well as the rationale for planning and using such statistical monitoring procedures.

In order to fulfil the ethical principles linked to the protection of patients randomized in a controlled clinical trial, monitoring procedures need to be set up. In this context, a committee of experts, called the data monitoring committee is in charge of reviewing regularly unblinded data to assess the quality and the relevance of the trial, to evaluate the evidence of an emerging treatment difference and to control the rate of occurrence of serious adverse events. After each meeting, the monitoring committee reports to the steering committee its recommendation to continue or to stop the trial prematurely. Protocol modifications might be proposed as well. Illustrated with several examples, this article reviews different situations a monitoring committee might have to tackle with.

The René Huguenin Cancer Center holds a medical file for each patient which is intended to store and process medical data. Since 1970, we introduced computerization: a development plan was elaborated and simultaneously a statistical software (Clotilde--GSI/CFRO) was selected. Thus, we now have access to a large database, structured according to medical rationale, and utilizable with methods of artificial intelligence towards three objectives: improved data acquisition, decision making and exploitation. The first application was to breast pathology, which represents one of the Center's primary activities. The structure of the data concerning patients is by all criteria part of the medical knowledge. This information needs to be presented as well as processed with a suitable language. To this end, we chose a language-oriented object, Mering II, usable with Apple and IBM 4 micro-computers. This project has already allowed to work out an operational model.