Cancer chemoprevention is defined as the use of natural or synthetic agents that reverse, suppress or arrest carcinogenic and/or malignant phenotype progression towards invasive
cancer.
Phytochemicals obtained from vegetables, fruits, spices, herbs and medicinal plants, such as
terpenoids,
carotenoids, flavanoids, phenolic compounds, and other groups of compounds have shown promise in suppressing experimental
carcinogenesis in various organs. Recent studies have indicated that mechanisms underlying chemopreventive action may include combinations of
anti-oxidant, anti-inflammatory, immune-enhancing, and anti-
hormone effects. Further, modification of
drug-metabolizing
enzymes, and influences on cell cycling and differentiation, induction of apoptosis, and suppression of proliferation and angiogenesis that play a role in the initiation and secondary modification of neoplastic development, have also been under investigation as possible mechanisms. This review will highlight the
biological effects of
terpenoids as chemopreventive agents on breast epithelial
carcinogenesis, and the utility of intermediate
biomarkers as indicators of premalignancy. Selected breast
chemoprevention trials are discussed with a focus on strategies for trial design, and clinical outcomes. Future directions in the field of
chemoprevention are proposed based on recently acquired mechanistic insights into breast
carcinogenesis.