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expert reaction to conference abstract about types of HRT and breast cancer risk

A conference abstract, presented at the 2019 San Antonio Breast Cancer Symposium, reports on the breast cancer risk associated with different types of HRT treatment.


Dr Melanie Davies, Chair, Fertility Preservation UK, and Consultant Gynaecologist, University College London Hospitals (UCLH), said:

What stage is this research? Can you judge if this is this good quality research and if the conclusions backed up by solid data? 

“Yes, this is high-quality research – the Women’s Health Initiative studies were carefully designed and government funded. The study design, a randomised placebo-controlled trial, is considered the ‘gold standard’ for comparison of interventions – in this case HRT versus no hormone treatment. The number of women entering and completing the trial was large.

How does this work fit with the existing evidence?

“Consistent in showing that HRT does influence breast cancer risk, but the finding of benefit from oestrogen-only HRT is surprising, see below.

“The extra information from this study is (a) the very long follow-up, showing that the effect of HRT persists more than 10 years after stopping it (b) that oestrogen and progestin have opposite effects on the breast, so that standard combined HRT increases cancer risk but oestrogen-alone reduces risk.

Have the authors accounted for confounders? 

“The RCT design should avoid this. Are there important limitations to be aware of? The main limitation is that the type of HRT used in WHI study, which started in 1993, is no longer available in UK. Modern forms of HRT may have different safety profiles – hopefully better, as modern HRT is more like the body’s own hormones.

What are the implications in the real world?

“This adds to the information available for women considering HRT, and in particular can reassure women who have had a hysterectomy and take oestrogen Is there any overspeculation? No, I don’t think so.

Why do these findings differ from those published in the Lancet by the Collaborative Group on Hormonal Factors in Breast Cancer earlier this year?

“Good question! The methodology is different. The WHI studies were randomised – whereas the Collaborative Group’s report was observational. The Collaborative Group did a meta-analysis (number-crunching) of 58 studies so they had a very large number of women, but the quality of observational research is much lower than RCTs. In the UK, NICE produced guidance on treatment of menopause in 2015 which carefully reviewed all the available research and noted the difference between the RCT and observational studies. 

What does this mean for women currently using HRT? Should they come off/change their type?



Long-term influence of estrogen plus progestin and estrogen alone use on breast cancer incidence: The Women’s Health Initiative randomized trials’ by Chlebowski et al. was presented at the 2019 San Antonio Breast Cancer Symposium at 13:30 UK time on Friday 13th December. 

There is no scientific paper as this is a conference abstract and presentation only.


Declared interests

Dr Melanie Davis: “I’m a consultant gynaecologist running an NHS menopause service, member of the Medical Advisory Council of the British Menopause Society, I contributed to the NICE guideline on Menopause, I do a small amount of private practice.”

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