What is Uterine Cancer?

Uterine cancer most often develops in the endometrium, the membrane that lines the inside of the uterus. For this reason, it is often called endometrial cancer. Although the cause of uterine cancer remains unknown, researchers believe that it develops when the uterus is exposed to too much estrogen and not enough progesterone—the two hormones involved in regulating the menstrual cycle.

Not surprisingly, many risk factors for uterine cancer in some way affect the level of estrogen that your uterus has been exposed to during your life. Among these factors are your age at menarche (first menstrual period), your age at menopause (last menstrual period), and whether you have used unopposed estrogen (hormone replacement therapy containing estrogen, but not progestin, a synthetic version of the hormone progesterone). About 95% of endometrial cancers develop in women age 40 or older; the average age at diagnosis is 60. Your risk increases if you started your periods before age 12 or underwent menopause after age 52, because this increases the number of years that your uterus has been exposed to estrogen. Your risk is higher if you have never given birth (because pregnancy provides a temporary break from the menstrual cycle) or if you are obese (because fat converts other hormones into estrogen, effectively raising your estrogen level).

If you are taking tamoxifen to help reduce your risk of breast cancer, you do face a small increased risk of endometrial cancer. Taking hormone replacement therapy after menopause should not increase your risk, as long as you are on a regimen that combines estrogen with progestin. If you have had breast or ovarian cancer in the past, or currently have diabetes, you are also at increased risk. Some families also carry genetic mutations that increase their risk, especially those related to hereditary nonpolyposis colon cancer, but this is relatively rare.

If you are still of childbearing age and would like to take steps to reduce your risk of uterine cancer due to a family history of the disease or other factors, talk with your healthcare provider about taking birth control pills. A large study by the CDC found that taking birth control pills for one year provided moderate protection against uterine cancer, and taking them for at least two years provided significant protection. The benefit remains for at least 10 years after you stop taking the pills. If you are considering taking postmenopausal hormone replacement therapy, make sure your prescription contains both estrogen and progestin.

SOURCE:
"Gynecologic Cancers." Preventing Cancer (Harvard Special Health Reports). Ann MacDonald in consultation with Graham A. Colditz, M.D., Dr.P.H. Stanford, CT: Harvard Health Publications, 2000.