Tamoxifen is one of a group of drugs called selective estrogen receptor modulators, or SERMs. Tamoxifen acts like estrogen on some tissues in the body, such as the uterus, but blocks the effects of estrogen on other tissues, such as the breast. Tamoxifen is used to prevent breast cancer in women who are at high risk for the disease. However, using tamoxifen for more than 2 years increases the risk of endometrial cancer. This risk is greater in postmenopausal women.
Raloxifene is a SERM that is used to prevent bone weakness in postmenopausal women. It does not have estrogen-like effects on the uterus and has not been shown to increase the risk of endometrial cancer. Other SERMs are being studied in clinical trials.
Hereditary nonpolyposis colon cancer syndrome
Hereditary nonpolyposis colon cancer (HNPCC) syndrome (also known as Lynch Syndrome) is an inherited disorder caused by changes in certain genes. Women who have HNPCC syndrome have a much higher risk of developing endometrial cancer than women who do not have HNPCC syndrome.
Other inherited conditions
Polycystic ovary syndrome (a disorder of the hormones made by the ovaries), and Cowden syndrome are inherited conditions that are linked to an increased risk of endometrial cancer.
Obesity increases the risk of endometrial cancer. This may be because obesity is related to other risk factors such as estrogen levels, polycystic ovary syndrome, lack of physical activity, and a diet that is high in saturated fats.
It is not known if losing weight decreases the risk of endometrial cancer.
The following protective factors may decrease the risk of endometrial cancer:
Combination oral contraceptives
Taking contraceptives that combine estrogen and progestin (combination oral contraceptives) decreases the risk of endometrial cancer. The protective effect of combination oral contraceptives increases with the length of time they are used, and can last for many years after oral contraceptive use has been stopped.
While taking oral contraceptives, women have a higher risk of blood clots, stroke, and heart attack, especially women who smoke and are older than 35 years.