An update on cancer prevention approaches

Majority of human cancers are caused, mediated and modified by environmental and lifestyle factors; and the multi-factorial, multi-step and multi-path process of carcinogenesis involves a series of genetic and epigenetic events. In spite of tremendous advancement in understanding of the molecular basis of cancer and identification of several environmental carcinogens, avoidance of exposure to carcinogens and early detection and/or successful treatment for most cancers have met with limited success. Based on the susceptibility to modulations of the multi-step process of carcinogenesis by a multitude of environmental compounds, lifestyle changes and host factors, and the demonstrated success of prevention of certain infectious diseases and cardiovascular events, cancer preventive interventions are receiving increasing attention. Several cancer preventive interventions such as vaccination, chemoprevention, weight control and lifestyle changes have been implemented. The current review focuses on several approaches and agents that have been scrutinized by way of randomized clinical trials in humans for their cancer prevention potential. Successful chemopreventive agents include selective oestrogen receptor modulators and aromatase inhibitors for breast cancer, the 5-α-reductase inhibitors for prostate cancer, non-steroidal antiinflammatory drugs (NSAIDs) for colorectal lesions and vaccines for viruses that are associated with cervical and liver cancers. Several experimentally proven chemopreventive agents have been observed to lack efficacy with and without toxicity. In spite of numerous chemoprevention trials, the number of successful agents is rather small. Identifying novel approaches and chemopreventives holds tremendous potential for reducing the burden of cancer.