Doctors and researchers are still trying to find out what causes cancer of the uterus (endometrial cancer). At present, they do not know why some women are affected while others are not. What is known is that certain risk factors are more common in women who get uterine cancer than in those who do not.
Having a risk factor doesn't mean you will develop uterine cancer. It only means that you have a higher risk than women who do not have the same risk factor. Only about half of women with uterine cancer have known risk factors.
Several of the following risk factors are related to an increased level of estrogen or longer exposure to estrogen. Estrogen is the hormone that controls the growth of the tissue that lines the uterus, which is where uterine cancer starts.
- Early menstruation or late menopause. Women who start having menstrual periods at age 12 or earlier have more periods than women who started menstruating after age 12. Likewise, women who reach menopause at an older age have more periods than those who have an earlier menopause. Having more periods means a woman has more exposure to estrogen, which can lead to a greater risk of uterine cancer.
- Never being pregnant. Women who have never been pregnant have a higher risk of getting uterine cancer. In pregnancy, progesterone levels rise and estrogen levels drop. This lowers the risk of uterine cancer.
- Estrogen therapy. Many women have used estrogen replacement therapy (ERT) to control menopause symptoms and to help prevent osteoporosis. But, ERT raises the risk of uterine cancer. For that reason, it is normally only given to women who don't have a uterus or who use a prescribed hormone called progesterone. Using a combination of estrogen and progesterone (called hormone replacement therapy, or HRT) does not raise the risk of uterine cancer.
- Obesity. Women who are overweight have twice the risk of getting uterine cancer as women of normal weight. Obese women have three times the risk of normal-weight women. Researchers believe estrogen may be the reason. Fat tissue changes other hormones into estrogen, so women with excess fat have larger amounts of estrogen.
- High-fat diet. Women who eat a diet high in animal fats have an increased risk of uterine cancer as well as other types of cancer. Experts think this may be because a high-fat diet can lead to obesity.
- Breast cancer drugs. Tamoxifen is a drug that may be prescribed to prevent or treat breast cancer. Tamoxifen blocks the effect of estrogen on breast tissue, but it acts like estrogen on uterine tissue, causing it to grow. Thus, tamoxifen may increase the risk of developing uterine cancer.The risk is relatively small (about one in 500), so for women at high risk for breast cancer the benefits of tamoxifen may far outweigh the risk of uterine cancer. However, women taking tamoxifen should be closely monitored and report any abnormal bleeding to their doctors.
- Diseases of the ovaries. Women who have polycystic ovary syndrome (PCOS) have a higher risk of uterine cancer.
- Family history of previous cancers. Women with a family history of endometrial cancer or an inherited type of colorectal cancer (heredity nonpolyposis colorectal cancer) have a greatly increased risk of uterine cancer.
Created on 11/16/1999
Updated on 09/22/2010
- National Cancer Institute. Endometrial cancer prevention.
- Bakkum-Gamez JN, Gonzalez-Bosquet J, Laack NN, Mariani A, Dowdy SC. Current issues in the management of endometrial cancer. Mayo Clinic Proceedings. 2008;83(1):97-112.
- American Cancer Society. What are the risk factors for endometrial cancer?