How does the type, dosage, and mode of delivery of postmenopausal hormones affect a woman's risk for breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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Growing epidemiologic data now address the effects of dose and type of estrogen on breast cancer risk. Data from the pooled analysis show no significant differences in the magnitude of risk were observed according to either the type of estrogen used (conjugated estrogen vs other) or the estrogen dose (< 0.625 vs ≥1.25 mg). Although the effect of estrogen use on breast cancer risk could be reasonably hypothesized to vary by mode of estrogen delivery (eg, patch estrogen, by avoiding the first pass effect in the liver, does not increase SHBG to the extent that oral preparations do), no important differences were observed in the largest study to date. The Million Women Study included over 40,000 users of transdermal estrogen and observed no significant difference in RR of breast cancer (1.24) compared to that among the 60,000 users of oral therapy (1.32). [46]

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