Clinical trials in cancer prevention: current results and perspectives for the future

Cancer prevention remains the ideal strategy for reducing the burden of cancer on society. Progress in cancer prevention has been accelerated as prevention clinical trials are completed and reported. A promising strategy is the identification of cancer risk factors through epidemiologic and experimental research with lifestyle and medical approaches that allow translation of clinical trial results to clinical practice. A major focus of cancer prevention clinical trials has been on modulation of hormones and nutritional modifications using natural or synthetic bioactive food components for breast and prostate cancer. Breast cancer prevention clinical trials have investigated the role of estrogen antagonists with agents such as tamoxifen, raloxifene, and newer agents such as aromatase inhibitors and bioactive food components. Among the promising bioactive food components being investigated at the National Cancer Institute in prevention clinical trials to reduce breast cancer risk are indole-3-carbinol, sulforaphanes, phytoestrogen isoflavones, perillyl alcohol, and green tea polyphenols. Prostate cancer prevention trials have focused on hormone modulation with the 5-alpha-reductase inhibitor finasteride and bioactive food components such as selenium and vitamin E. Soy isoflavones, green tea polyphenols, and doxercalciferol also are being investigated for prostate cancer prevention. Future prevention clinical trials will rely on multidisciplinary medical approaches that bring together expertise in many fields to address disease across the cancer spectrum. Nutritional science can play an important role in this effort through the use of new and emerging technologies to better understand the influence of bioactive food components on the genes, proteins, and cellular processes that are associated with cancer risk.