One of the roles of naturally occurring estrogen is to promote the normal growth of cells in the breast and uterus. For this reason, it is generally believed that menopausal estrogen use by women who have already been diagnosed with breast cancer may promote further tumor growth. Studies of hormone use to treat menopausal symptoms in breast cancer survivors have produced conflicting results.
In one trial, 434 breast cancer survivors receiving either estrogen alone or estrogen plus progestin were followed for 2 years before the study was stopped because researchers concluded that even short-term use of hormone replacement therapy posed an unacceptable risk of breast cancer recurrence. Among these study participants, 26 women in the group receiving hormone replacement therapy had another occurrence of breast cancer compared with 7 women in the group receiving no hormone replacement therapy. In another study, which included 378 women who were followed for 4 years, 11 women receiving hormone replacement therapy had another occurrence of breast cancer compared with 13 women receiving no hormone replacement therapy, so the risk of breast cancer recurrence was not increased. A review of 15 studies comprising a total of 1,416 breast cancer survivors and 1,998 women without a history of breast cancer found no increase in risk of cancer recurrence with hormone replacement therapy use.
There is limited research on the risks associated with menopausal hormone use by women who have had other cancers, particularly gynecological cancers. One review of the published research found that no firm conclusion could be drawn about the safety of hormone use in women with a history of cancer. However, survivors of gastric and bladder cancer and meningioma may be at higher risk of a recurrence. Survivors of gynecological cancers may be at higher risk because these cancers tend to be more hormone-dependent, but more studies are needed.
This information is produced and provided by the National Cancer Institute (NCI). References are available at their website at www.cancer.gov. The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via www.cancer.gov or call 1-800-4-CANCER.