Special aspects of cancer prevention trials.

Abstract

The results of early cancer prevention trials now are being reported, and new trials have begun or are being designed. Initial trials used agents such as vitamins and minerals, generally regarded as safe. The trials in progress are using similar agents or macronutrient manipulation, but some have incorporated drugs with low but definite toxic potential, such as tamoxifen. Appropriate prevention trial design requires careful consideration of agent toxicity and the use of such agents in healthy individuals. Full disclosure of risks and benefits to potential subjects is necessary. Other considerations are study duration (usually very long) and subject number (usually very large), both of which increase the cost of a trial. Successful prevention trials must overcome these barriers through innovative design. Possible innovations include the use of intermediate marker end-points, the enrollment of subjects at high risk for a specific cancer, and the use of volunteers to help conduct trials.