This is important since imbalances in hormone biotransformation (e.g., inefficient methylation by catechol O-methyltransferases; COMT) are implicated in the initiation of breast cancer through the generation of genotoxic metabolites (i.e., estrogen quinones) and reactive oxygen species (ROS), and the depletion of vital antioxidants and metabolic cofactors. This evidence concerns the gene COMT and breast carcinoma.