CYP1A2 and breast cancer: The genetic polymorphism may only affect postmenopausal women with low body fat, low endogenous estrogens, and relatively low CYP1A2 activity, whereas the higher estrogen levels and CYP1A2 activity in women who use HRT [28], will develop breast cancer [29], or are overweight [30] may outweigh any changes in hormone patterns due to the CYP1A2 variant alleles.