Additional Evidence that Estrogen Alone Increases the Risk of Endometrial Cancer

Additional Evidence that Estrogen Alone Increases the Risk of Endometrial Cancer

A study published in the American Journal of Epidemiology provides additional evidence that postmenopausal hormone therapy consisting of estrogen alone increases the risk of endometrial (uterine) cancer in women who have not had a hysterectomy. Consistent with most previous studies, use of combined estrogen plus progestin did not increase the risk of endometrial cancer.

As women reach menopause and beyond, more than 80% will experience symptoms such as hot flashes, night sweats, sleep disturbance, and vaginal dryness.[1] Estrogen, with or without progestin, is the most effective treatment for many of these symptoms.[2] Recent studies, however, have raised concerns about the health effects of postmenopausal hormone therapy.

Use of estrogen plus progestin has been linked with an increased risk of heart disease, breast cancer, stroke, and blood clots and a decreased risk of fractures and colorectal cancer.[3] Use of estrogen alone has been linked with an increased risk of strokes and a decreased risk of fractures.[4] In women with a uterus, use of estrogen alone has also been linked with an increased risk of endometrial (uterine) cancer. For this reason, estrogen alone is commonly reserved for women who have had a hysterectomy.

To further explore the links between postmenopausal hormone therapy and risk of endometrial cancer, researchers conducted a study among 511 postmenopausal women with endometrial cancer and 1,412 postmenopausal women without endometrial cancer.

  • Compared to women who had never used postmenopausal hormone therapy, women who had used estrogen alone for three years or more were more than three times more likely to develop endometrial cancer.
  • Use of combined estrogen plus progestin did not increase the risk of endometrial cancer.
  • Risk of endometrial cancer was significantly lower among women who used combined estrogen plus progestin than among women who used estrogen alone.

Consistent with previous reports, this study suggests that use of estrogen alone increases the risk of endometrial cancer in women who have not had a hysterectomy. Also consistent with most previous reports, the study found that use of combined estrogen plus progestin did not influence the risk of endometrial cancer.

Reference: Strom BL, Schinnar R, Weber AL et al. Case-control Study of Postmenopausal Hormone Replacement Therapy and Endometrial Cancer. American Journal of Epidemiology. 2006; 164:775-786.

[1]Gracia CR, Freeman EW. Acute consequences of the menopausal transition: the rise of common menopausal symptoms. Endocrinol Metab Clin N Am. 2004;33:675-689.

[2]NIH State of the Science Panel. National Institutes of Health State-of-the-Science Conference Statement: Management of Menopause-Related Symptoms. Ann Intern Med. 2005; 142:1003-1013.

[3]Rossouw JE, Anderson GL, Prentice RL et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA. 2002; 288:321-33.

[4]Anderson GL, Limacher M, Assaf AR et al. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women’s Health Initiative randomized controlled trial. JAMA. 2004; 291:1701-1712.

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