Menopause and the Risk of Breast Cancer

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Abstract
In summary, although there is a fair amount of inconsistency regarding the effects of menopausal estrogen therapy on the risk of breast cancer, this may relate to inability of some studies to fully assess effects related to long-term and/or high-dosage usage, the exposures that appear to be most consistently related to elevations in breast cancer risk. Many relationships, however, remain unresolved. For example, there is only scant epidemiologic information available on the relationship of breast cancer risk to exposure to estrogens in forms other than pills, such as injectable estrogen cream, or patches. Also unclear is whether different estrogens have discrepant effects. For example, in the recent Swedish study, the primary estrogen prescribed was estradiol, a more potent estrogen than the conjugated estrogens commonly prescribed in the United States. Few studies, all based on limited numbers of exposed women, have provided data regarding effects of combined estrogen/progestin therapy, and further investigations are vitally needed to assess effects on breast cancer risk of progestins added to the commonly used estrogens in this country, including conjugated estrogens and diethylstilbestrol. Given the absence of information on the risks of breast cancer associated with menopausal estrogen therapy, especially when combined with progestins, it is extremely difficult to develop counseling approaches and for informed decisions to be made. Decisions must be made, recognizing that there are considerable benefits that have been associated with estrogen therapy, including substantial reductions in the risk of both osteoporosis and certain cardiovascular diseases. However, many relationships of risk with specific patterns of usage remain unresolved, particularly with respect to the effects on risk of combined estrogen/progestin therapy.