What is the increased risk of breast cancer in women with a history of postmenopausal hormone use?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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Although some aspects of the relationship between postmenopausal hormones and breast cancer risk remain unresolved, several areas of clear agreement have emerged. Combination estrogen plus progestin therapy is carcinogenic in women and causes breast cancer. The adverse effect of combination therapy is greater than that observed for estrogen alone. Whether some forms of progestin are safer remains under study.

Overall, the findings indicate an increased risk in two important subgroups of users: users of long duration and current users. In general, users of long duration are more likely to be current users, so, in many studies, these two groups overlap substantially. From a biological perspective, these are the groups one would most expect to demonstrate a relationship with breast cancer risk, as exogenous estrogens appear to act as a promoter at a late stage.

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