Criteria of evidence to move potential chemopreventive agents into late phase clinical trials

Preclinical models and data from clinical trials suggest that cancer is a preventable disease. However, demonstration of a preventive effect requires large phase III clinical trials of long duration and involves many thousands of participants. The decision to proceed with phase III studies therefore must be informed by robust efficacy and safety data. This requires a systematic review of all available preclinical, epidemiological, and clinical data, along with a mechanistic understanding of the biology of the disease under study. In this review we identify the issues that are critical to decision-making prior to embarking on late phase prevention clinical trials and provide a framework for making such decisions.