Hormone replacement therapy and risk for breast cancer

A number of methodologic difficulties have prevented clear interpretation of the effects of menopausal estrogens on breast cancer risk. Some studies show that the risk may be elevated among either long-term users or recent users, but results are not entirely consistent. Further complicating this interpretation is the recent trend toward prescribing estrogens in conjunction with a progestin. Dissimilar to endometrial cancer, it does not appear that this regimen eliminates any risk associated with estrogens alone, but whether combined therapy actually has an adverse effect on breast tissue has yet to be resolved. Also requiring further investigation is whether certain subject characteristics alter the effects of hormones, including a family or personal history of breast cancer.