Clinical effects of A4889G and T6235C polymorphisms in cytochrome P-450 CYP1A1 for breast cancer patients treated with tamoxifen: implications for tumor aggressiveness and patient survival.

Purpose: Individual differences in cytochrome P-450 efficiency partly explain their variations in resistance to tamoxifen and estrogen metabolism. Two polymorphisms of the CYP1A1 gene-A4889G and T6235C-are known to affect activation of estrone and estradiol and to deregulate concentration of highly active tamoxifen metabolites. However, the clinicopathologic implications of these findings have not yet been evaluated.