Phase II cancer prevention clinical trials.

The development of agents to prevent cancer requires an iterative process of target identification, preclinical testing, and early and late phase clinical trials to establish efficacy and safety. Since phase III definitive efficacy trials with cancer endpoints require a lengthy timeframe and considerable resources for completion, it is critical to first optimize agent delivery and trial design and to determine preliminary efficacy via the conduct of phase II trials. Phase II trials vary considerably in their endpoints, cohorts, and designs due to differences in the process of carcinogenesis and ability to sample tissues across different target organs. However, the goal of all such trials is to provide evidence of interference with the development of cancer and to identify safety signals that would limit the benefit from interventions. Published by Elsevier Inc.