ABSTRACT
In this review, we summarize the epidemiologic evidence for the associations of oral contraceptives and postmenopausal hormones with risk of breast cancer. We also describe the biologic plausibility of these relationships. Overall, there appears to be little, if any, increase in risk with oral contraceptive use in general, even among users for 10 or more years. However, compared to never users, current oral contraceptive users appear to have a modest elevation in risk that subsides within about 10 years after cessation of use. For postmenopausal hormones, the weight of the evidence suggests little or no increase in risk among users of short duration, or for use in the past. However, current longer term use is associated with an increased risk of breast cancer that increases with duration. This increase in risk is large enough, and well enough supported, to be considered along with the other risks and benefits of postmenopausal hormone therapy.