Women who take menopausal hormone therapy face a significantly increased risk of developing breast cancer, according to the findings of a major study published today.
Researchers found that among women who took oestrogen with daily progestogen 2% extra developed breast cancer by the age of 70.
They studied the effect of taking treatments from the age of 50.
The research, published in The Lancet, found that among those who took oestrogen with intermittent progestogen, there were one in 70 extra cases of breast cancer.
When the treatment was only oestrogen, the proportion developing breast cancer increased by 0.5%.
The only treatment not linked to increased risk was topical vaginal oestrogen.
The findings come from an analysis of 100,000 women involved in 58 epidemiological studies around the world between 1992 and 2018.
Use of menopausal hormone treatments halved at the beginning of the century following early studies – but has since stabilised.
Researcher Professor Valerie Beral, from the University of Oxford, UK, said: "Our new findings indicate that some increased risk persists even after stopping use of menopausal hormone therapy. Previous estimates of risks associated with use of menopausal hormone therapy are approximately doubled by the inclusion of the persistent risk after use of the hormones ceases."
The UK Royal College of Obstetricians and Gynaecologists said the conclusions were "not new."
Vice-president Professor Janice Rymer said: “The findings from this research should be helpful to both women and doctors, particularly around when considering whether to start hormone therapy, for how long and which preparation they could take – whether it includes oestrogen and progestagen combined, or oestrogen alone. These findings should not put women off taking HRT if the benefits – such as protection of bones and decrease in cardiovascular risk – outweigh the risks.
“To put the risk into context, a woman has greater risk of developing breast cancer if she is overweight or obese compared to taking HRT. Women must be aware of the effect of obesity and alcohol which increase the risk of breast cancer and modifies the additional risk of HRT.”
UK Royal College of GPs vice-chair Professor Martin Marshall said: “The link between HRT and an increased risk of breast cancer has been known for some time. But it is a complex relationship, and only relates to preparations of HRT that contain certain progestogens – the addition of which is necessary for women who have not had a hysterectomy – and it appears that some combined HRT preparations have a higher breast cancer risk than others.
“This research highlights the importance of taking a holistic approach to prescribing, considering all the different factors potentially affecting an individual’s health and wellbeing, which is what GPs are highly trained to do. It also demonstrates how vital it is that patients are involved in decision-making about their health, fully-informed about the various risks and benefits associated with a treatment."
Dr Julie Sharp, from Cancer Research UK, said: “It’s important to put the risk in perspective – HRT causes 1,400 cancers a year in the UK, which is less than 1% of cases. We need high quality, accurate information on the long-term effects of using HRT, which is why we’ve funded this research; women have to know the risks of which type of HRT they take and how long they take it for to decide what’s right for them."
Lancet 30 August 2019
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)31709-X/fulltext
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