Despite significant advances in the treatment of many tumors, the battle against cancer is far from being won. It has become increasingly obvious that the problem of cancer cannot be solved by treatment alone, and an alternative approach is needed. Although the carcinogenic process may be driven by mutations, many epigenetic variables can
also be important determinants during the 20-year (or more) latent period before invasion and metastasis occur (Sporn, 2000). Modulation of these regulatory pathways, as well as blocking mutagenic damage to DNA, offers great potential for the prevention of cancer. The traditional approach to cancer prevention has consisted of attempts to eliminate carcinogenic agents and to detect and remove precancerous lesions. Currently, efforts are increasingly focused on interrupting, reversing, or delaying the neoplastic process. This approach not only complements therapeutic modalities currently in use but may provide alternatives for combating tumors that are unresponsive to treatment (Itri, 1993). Hence, cancer chemoprevention or reversal of carcinogenesis in the premalignant phase can be defined as the use of natural or synthetic chemicals to suppress, delay, or prevent the process of carcinogenesis.