• Dr. Paul Raas

Menopausal hormone therapy: why we should no longer be afraid of the breast cancer risk.

I copied this title from an article I read from Dr.

Tan. I want to thank him for providing me with the original manuscript.

When I discuss MHT (Menopause Hormone Treatment) with a patient in my office, one of the first questions she will ask is: "What about the breast cancer risk?".

I guess the threat of breast cancer is the main reason women are afraid to go on hormones.

In 2002, the Women's Health Initiative (WHI) stopped the oestrogen-progestin arm after a mean of 5.2 years because of the higher incidence of breast cancer. At the same time, the same study found a significant decrease of over 20% in breast cancer among participants on oestrogen only. I remember our surprise very well, as we always believed oestrogen was the driving proliferative hormone.

This event caused a steep decline in MHT use; colleagues feared prescribing MHT because of possible legal consequences.

This decline has so far remained very difficult to reverse.

You need to know the following:

1. Breast tumours most likely grow in the body for up to 5 years or even more before we can detect them as breast cancer. Hormone receptor-positive breast cancer will grow faster under MHT. Scientists expected that in the first years, due to this phenomenon, we would find more breast cancer in the women starting to take hormones because they already had breast cancer, and it was growing faster. In women, without hormones, on the contrary, we would detect them years later.

2. In the WHI study, hormones prescribed were almost exclusively conjugated equine oestrogens (CEE), either alone or combined with medroxyprogesterone acetate (MPA). I'm not particularly eager to prescribe these hormones. Conjugated equine oestrogens are predominantly prescribed in the USA, Canada and England, as far as I know. Isolating oestrogens from pregnant mares' urine gave rise to an enormous hormone industry. Equine (horses) oestrogens contain certain oestrogens that we humans do not produce and therefore are not natural to us.

3. In Central Europe, we would instead use bio-identical 17-beta-oestradiol or oestriol.

We used progestin (synthetic progestogen) in the early years of the combined treatment. For many years now, I would say more and more since 2000; we have used micronized progesterone.

Evidence-based discussion:

1. Does Menopause Hormone Treatment at the time of detection or even before higher the risk of breast cancer mortality?

NO. Precisely the opposite. Hormone treatment reduces the risk!

I like to point to the following article from Mikkola TS: Reduced risk of breast cancer mortality in women using postmenopausal hormone therapy: A Finnish nationwide comparative study.

In total, 489,105 women using MHT from 1994 to 2009 were followed from the MHT initiation (3.3 million cumulative exposure years) to breast cancer death (n = 1,578 women). The authors compared the observed deaths with those in the age-standardized background population.

In the Finnish unselected population, breast cancer is fatal in 1 of 10 patients and reduced to 1 of 20 patients with a history of MHT use. This observation is an important message for women considering or already using MHT.

2. In the literature I reviewed, there is no difference in breast cancer incidence or mortality using conjugated equine oestrogens versus bio-identical oestradiol.

3. A 2017 review of 14 studies concluded that using oestrogen combined with micronized progesterone (odds ratio [OR] 1.00, 95% CI 0.8–1.2) carries no greater risk for breast cancer.


The WHI results from 2002 are historical and should no longer be relevant to current practice.

Women who develop breast cancer while using MHT have a reduced risk of dying from it.

Oestrogen combined with micronized progesterone carries no greater risk for breast cancer.

D A Tan, A R B Dayu: Menopausal hormone therapy: why we should no longer be afraid of the breast cancer risk

Climacteric: the Journal of the International Menopause Society 2022 February 11, 1-7

Mikkola, Tomi & Savolainen-Peltonen, Hanna & Tuomikoski, Pauliina & Hoti, Fabian & Vattulainen, Pia & Gissler, Mika & Ylikorkala, Olavi. (2016). Reduced risk of breast cancer mortality in women using postmenopausal hormone therapy: a Finnish nationwide comparative study.

Menopause. 23. 1. 10.1097/GME.0000000000000698.

P. Stute, L. Wildt & J. Neulen (2018) The impact of micronized progesterone on breast cancer risk: a systematic review,

Climacteric, 21:2, 111-122, DOI: 10.1080/13697137.2017.1421925

Yang Z, Hu Y, Zhang J, Xu L, Zeng R, Kang D: Estradiol therapy and breast cancer risk in perimenopausal and postmenopausal women: a systematic review and meta-analysis.

Gynecol Endocrinol. 2017 Feb;33(2):87-92. doi: 10.1080/09513590.2016.1248932. Epub 2016 Nov 29. PMID: 27898258.

Dr. Paul Raas

31 Aug. 2022