Low-Dose Estrogen May Increase Risk Of Endometrial Cancer
LONDON, ENGLAND -- May 28, 1999 -- Hot flushes and night sweats are common early in the menopause. To prevent these symptoms many women take preparations of the female sex hormone, estrogen, usually with a progestagen, another class of sex hormones that counteract estrogen's growth-stimulating effect on the lining of the uterus (the endometrium), which can increase the risk of endometrial cancer.
Later in the menopause, however, many women develop atrophy of the tissue that lines the vagina and urethra (the vaginal and urethral epithelium). For these symptoms, many doctors prescribe low-potency estrogen preparations that can be taken by mouth or administered intravaginally. These estrogen preparations are not thought to increase the risk of endometrial cancer.
However, the results of a study in this week's issue of The Lancet indicate that low-potency estrogen preparations may in fact increase the risk of cancer.
A Swedish research team, led by Dr. Elisabete Weiderpass of Stockholm's Karolinska Institutet, report that compared with women who had never used estrogens, women who had used low-potency oestrogen pills had a two-fold increased risk of endometrial cancer. They also found that women who had used the pills for five years or longer had a greater than three-fold increased risk of endometrial cancer and an eight-fold increased risk of having abnormal endometrial cell growth (atypical hyperplasia). Although there was some evidence that vaginal estrogens might increase risk, the statistical association was not strong. The researchers also found that the increased risk associated with the oral estrogens disappeared rapidly once a woman stopped taking the pills.
The researchers also compared the medical histories of 709 women who had had endometrial cancer with 3,368 women who had not developed the disease. The low-potency regimens they assessed were oral estriol and vaginal dienestrol, estriol or estradiol.
"Oral, but not vaginal, treatment with low-potency oestrogen formulations increases the relative risk of endometrial neoplasia," the researchers write. "Close surveillance of patients is needed and addition of a progestagen should be considered."
Related Links: The Lancet
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