The World Health Organization defines hormone replacement therapy as carcinogenic: is this plausible?

Our plain-English summary of The World Health Organization defines hormone replacement therapy as carcinogenic: is this plausible?, by A.O. Mueck, H. Seeger (Gynecological Endocrinology, 2008).

The study

• Authors: A.O. Mueck, H. Seeger
• Journal: Gynecological Endocrinology
• Published: 2008;24(3):129-32
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In June 2005 the World Health Organization's International Agency for Research on Cancer (IARC) classified combined hormone contraception and menopausal therapy as carcinogenic in humans. The IARC's function is to identify potential carcinogens associated with nutrition, environment and pharmaceutical products. They do not produce risk-benefit analyses for any country or population. Their conclusions are highly controversial in that no proof is presented for a causal relationship of estrogens with reproductive cancer, be it plausibility according to mechanisms of action or experimental evidence in an animal model. Equating natural compounds like estradiol with defined carcinogens like asbestos, tobacco smoke as well as indispensable drugs such as aspirin and tamoxifen is of no substantial clinical relevance. Thus, there are no new reasons to change current management principles with combination hormone contraception and therapy.

In plain English

This was an opinion paper from the Department of Endocrinology and Menopause at a university women's hospital in Tuebingen, Germany. It was not a study of asbestos exposure. Asbestos was mentioned only as a comparison. The authors discussed the June 2005 decision by a Working Group of the International Agency for Research on Cancer (IARC) to classify combined oral contraceptives and combined estrogen–progestogen menopausal therapy as carcinogenic in humans (Group 1). They noted that the IARC had not found these products carcinogenic in 1987 or 1999. They argued that standard tests had not shown that these hormones cause gene mutations. Describing another study, the Women's Health Initiative trial, they reported a small absolute excess of breast cancer with combined therapy: three, four and seven cases per 1000 women over 5 years at ages 50–59, 60–69 and 70–79. The authors concluded that estradiol should not be equated with asbestos or tobacco smoke, that there were no new reasons to change current management with hormone therapy, and that absolute rather than relative risks should be cited.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: opinion paper commenting on an IARC classification and on published research; not an original study
• Who was studied: No study population. The paper discussed the IARC Working Group's June 2005 evaluation of combined oral contraceptives and combined estrogen–progestogen menopausal therapy, and published studies on these.
• Exposure: Combined estrogen–progestogen hormone contraception and menopausal hormone therapy. Asbestos was mentioned only as a comparison with other substances classified as carcinogens.
• Main results:
  • The authors noted that in 1987 and 1999 the IARC had not found combined oral contraceptive or HRT use to be carcinogenic.
  • The authors stated that standardized mutagenicity tests with the endpoint of gene mutation had not provided proof of any mutagenic action.
  • Citing the Women's Health Initiative trial (another study), the authors reported an excess risk with combined therapy of three breast cancer cases per 1000 women at ages 50–59, four at 60–69 and seven at 70–79, over 5 years on an intention-to-treat basis.
• The authors' conclusion: The authors concluded that estradiol should not be equated with asbestos or tobacco smoke, that there were no new reasons to change current management principles with HRT, and that absolute rather than relative risks should be cited.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, IARC.

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