The concept of an overview of cancer clinical trials with special emphasis on early breast cancer.

Overviews are valuable investigations that require international cooperation, and can provide a useful summary of available information on a current therapeutic issue. Combining results of trials in early breast cancer is an appropriate example of such procedures. However, the advantage of bringing a large amount of information together might be overcome by the disadvantages of improper conduct and overinterpretation of the overview findings. A prospective protocol must be prepared and followed. The results must be presented in sufficient detail to allow independent conclusions to be reached. The influence of strict application of the arithmetic construct must be recognized when determining whether the conclusions about the impact of separate components of treatment are appropriate. Most importantly, the transition from scientific inquiry to the application of treatment recommendations for individual patients must still be made very cautiously. We stress the importance of the results from individual, well-conducted clinical trials for providing the critical information for guiding the choice of treatment for patients outside of trials.