Taking tamoxifen for breast cancer or taking estrogen alone (without progesterone) can affect the risk of developing uterine (endometrial) cancer.
Endometrial (uterine) cancer may develop in breast cancer patients who have been treated with tamoxifen. A patient taking this drug should have a pelvic exam every year and report any vaginal bleeding (other than menstrual bleeding) as soon as possible. Women taking estrogen (a hormone that can affect the growth of some cancers) alone have an increased risk of developing uterine (endometrial) cancer. Taking estrogen in combination with progesterone (another hormone) does not increase a woman’s risk of uterine cancer.