Uterine cancer: Who's at risk?
At the age of 59, Mrs. K. thought she was done with menstrual periods. When she developed slight vaginal spotting, she promptly sought the advice of her gynecologist, who assured her that only a small proportion of women who experience post-menopausal bleeding have a serious condition.
Yet after an in-office biopsy of the uterine lining, she was surprised to find the results showed that she had uterine cancer.
In the United States, uterine cancer is the most common of the gynecologic cancers. Approximately 50,000 American women develop this disease of the female reproductive tract every year, with the average woman having a 2.6% lifetime risk of developing uterine cancer.
Fortunately, like Mrs. K., most women with uterine cancer experience bleeding early in the natural history of the disease, leading to early diagnosis, when a complete cure is possible with proper treatment.
Most cancers of the uterus develop in the uterine lining, or endometrium, and are referred to as endometrial cancers. These cancers most often develop in women post-menopause, with the average age of diagnosis about 61.
Although there are several types of endometrial cancer, the most common kind is caused as a result of long-term exposure to estrogen, one of the main female hormones, that is not balanced by exposure to progesterone, another important female hormone. We call this situation exposure to unopposed estrogen. Factors that increase the risk of endometrial cancer are mostly those that produce prolonged exposure to unopposed estrogen. These include:
Obesity The most common risk factor is simply being overweight post-menopause. Following menopause the ovaries no longer produce eggs or progesterone, which counteracts the stimulation of the uterine lining by estrogen. Although ovarian estrogen production falls dramatically after menopause, women continue to produce estrogen in the fatty tissues of their bodies. Therefore, overweight women will have higherlevels of estrogen, and over a period of years the hormone can stimulate overgrowth of the lining of the uterus and cause a cancer to form.
Estrogen Medications. This risk may include both estrogens given by pill or patch, and so-called natural estrogens including phytoestrogens, which are derived from plants. Women who use low dose estrogen therapy in the form of vaginal pills or creams, however, are not at increased risk of uterine cancer. Women who take tamoxifen, a weak estrogen often given to treat or prevent breast cancer, do experience an increased risk for endometrial cancer, so abnormal bleeding should be promptly investigated in these patients. It is important to note that the use of birth control pills, which contain progesterone, actually decreases the risk of endometrial cancer, as do progesterone containing contraceptive implants.
Excess Estrogen Production by the Ovaries A less common cause of endometrial cancer is a condition seen in younger women called polycystic ovary syndrome. These women are typically overweight and do not ovulate, so they are at increased risk for endometrial cancer due again to unopposed estrogen, produced both in their ovaries and fatty tissue. Rarely, women may develop an ovarian tumor that produces high levels of estrogen, resulting in endometrial cancer.
Family History Although most cases of endometrial cancer are not hereditary, about 5% occur in women who carry genes for Lynch Syndrome. This condition puts them at greatly increased for a number of cancers, including uterine, ovarian, and gastrointestinal cancers. Lynch syndrome can be transmitted from parents (including fathers) to children (including sons). Women who have a strong family history of cancer should seek genetic counseling to be evaluated for hereditary cancer syndromes, including Lynch Syndrome.
Stephen C. Rubin, M.D. is a professor and chief of the division of gynecologic oncology at Fox Chase Cancer Center.
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