Researchers affiliated with the Women’s Health Initiative (WHI) have reported that hormone replacement therapy (HRT) increases the risk of breast cancer and lung cancer among postmenopausal women. These results were recently published in the March 5, 2008 issue of the Journal of the American Medical Association.

Postmenopausal HRT (combined hormone therapy) effectively manages several common menopausal symptoms.  However, recent studies have reported an increase in the incidence of breast cancer among women taking HRT, an event leading to a discontinuation of this therapy in most women. A large clinical trial conducted as part of the WHI raised concerns about the health risks of HRT. In 2002, for example, it was reported that combined estrogen plus progestin increases the risk of breast cancer, heart disease, stroke, and blood clots. Women taking estrogen plus progestin had fewer fractures and were less likely to develop colorectal cancer, but for most women, these benefits were thought to be outweighed by the risks. Researchers continue to evaluate long-term data from this trial.  

Researchers affiliated with the WHI recently evaluated data from the WHI trial to determine if hormone therapy affected the risk of developing breast and other cancers. The WHI trial included almost 16,000 postmenopausal women who were treated with HRT or placebo. Endpoints were measured during treatment and three years after cessation of HRT.

• Cardiovascular effects were increased during the administration of HRT, but at three years were similar between women treated with HRT and those who received placebo.
• Overall, the risk of developing any type of cancer was 24% higher among women treated with HRT compared with those who received placebo. However, the risk of developing endometrial and colorectal cancer was lower than in women receiving placebo.
• The rates of breast cancer and lung cancers were increased 27% in the HRT group.
• There were 101 cancer-related deaths in the HRT group and 69 in the placebo group. However, most deaths were not related to breast, colorectal, endometrial, or ovarian cancer.
• All-cause mortality was the same during HRT administration, but was 15% higher after discontinuation.

The researchers concluded that the use of HRT significantly increases the risk of developing fatal and nonfatal malignancies after HRT has been discontinued.

Comments: These data confirm that the risks of HRT outweigh the benefits.

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Reduction in Hormone Replacement Therapy Linked to Drop in Breast Cancer Cases (12/19/2006)

Hormone Use Also Increases Risk of Breast Cancer in Black Women (5/1/2006)

Hormone Replacement Therapy Decreases Incidence of Localized but not Regional or Metastatic Colon Cancer (3/4/2004)

The Million Women Study Documents Risks of Death From Breast Cancer Following Hormone Replacement (8/11/2003)

Breast Cancer Risks of Hormone Replacement Therapy Defined (6/30/2003)

Estrogen Replacement Therapy May Not Increase Recurrences in Hormone Receptor Negative Breast Cancer (10/30/2002)

U.S. Preventive Services Task Force Issues Recommendations for Hormone Replacement Therapy (10/23/2002)

Hormone Replacement Therapy is Associated with Early Detection and Better Survival From Breast Cancer (9/19/2002)

Long-term Continuous Combined Hormone Replacement Therapy with Estrogen and Progesterone is not Associated with Uterine Cancer (8/14/2002)

Long Term Hormone Replacement with Estrogen is Associated with Increased Risk of Ovarian Cancer (7/31/2002)

Lack of Benefit and Potential Harm Halts Clinical Trial of Hormone Replacement for Post-Menopausal Women (7/10/2002)

Hormone Replacement Therapy (HRT) May Be Associated with Increased Risk of Ovarian Cancer (4/8/2002)

Long-Term Use of Hormone Replacement Therapy Increases Risk of Breast Cancer (3/5/2002)

Reference: Heiss G, Wallace R, Anderson G, et al. Health risks and benefits 3 years after stopping randomized treatment with estrogen and progestin. Journal of the American Medical Association. 2008; 299:1036-1045.