ABSTRACT
The randomized clinical trial is an elegant and simple concept. In theory an investigator has only to identify a study group, choose an intervention and control, and wait until enough outcome events have occurred. Clinical trials of cancer prevention are a recent undertaking , and to our knowledge, none of any size has yet been completed. It is difficult, therefore, to judge and impossible to know which strategies will be more or less likely to yield success in carrying out these studies. Studies of cancer-preventive strategies will usually need to be large clinical trials, both because the study outcomes will be relatively rare and because the probable effects of the intervention will be modest at best. The need for a large sample size often requires that the study be a collaborative multicenter endeavor, which entails administrative complexity. The principal factors in choosing a population for study are discussed elsewhere in this text.
