01-07-2025
Drug taken by millions of women could raise breast cancer risk in young women, study finds
Giving younger women certain types of hormone replacement therapy could raise their breast cancer risk, concerning research today suggested.
The treatment, also known as HRT, was first linked to the disease more than two decades ago, with debate about its safety causing confusion and concern for millions of women ever since.
Most studies examining the risk have been explored in older women, who take it to help menopause symptoms. In the young it is often taken after gynaecological surgery or during perimenopause.
But US scientists have now discovered that oestrogen plus synthetic progesterone HRT increased the risk of breast cancer in women under 55 by a tenth.
Yet, oestrogen HRT alone appeared to decrease the risk by almost a sixth.
Experts today, who labelled the findings important, said they should now influence a clinician's decision whether to prescribing the drug to certain women is the best course of action.
They did, however, caution that the risk of developing breast cancer due to HRT remains 'small' and is 'outweighed by the benefits'.
Writing in the prestigious journal Lancet Oncology, scientists at the National Institute of Environmental Health Sciences, based in North Carolina, said: 'The findings can be used to augment clinical recommendations for hormone therapy use in young women, for whom guidance was previously scarce.
They added: 'Oestrogen [only] hormone therapy use appears to decrease breast cancer risk and oestrogen plus progesterone appears to increase breast cancer risk.'
Back in 2018, fewer than 1.3 million NHS patients were being prescribed HRT, a safe and cheap medicine proven to effectively combat the most debilitating menopause symptoms.
Today this figure has doubled, with about 2.6 million women now on the medication, which replenishes the female sex hormones oestrogen and progesterone that are lost during the menopause.
There are different types of HRT available which contain different hormones—some are oestrogen alone, others contain progestogen while a third type contains both—and can be taken in the form of gels, patches or pills.
Previous research has suggested women who have already been through the menopause have an increased risk of breast cancer taking oestrogen plus progesterone HRT, due to longer exposure to the hormone.
In the fresh study, scientists examined data drawn from previous studies of 459,476 women aged 16 to 54 years old.
Two per cent of this group (8,455) developed young-onset breast cancer, which means the disease was diagnosed before they were 55 years old.
Some 15 per cent of women involved in the study reported using HRT, with oestrogen plus progestin HRT and oestrogen HRT being the most common types.
They found that oestrogen appeared to reduce the risk of young breast cancer by 14 per cent while oestrogen plus progestin therapy increased risk by 10 per cent.
Responding to the findings, Dr Kotryna Temcinaite, head of research communications at the charity Breast Cancer Now, said: 'This large scale study offers useful insights for women aged under 55.
'These results are largely in line with what we already know about taking HRT for menopausal symptoms and its effects on breast cancer risk—for most people, the risk of developing breast cancer because of taking HRT is small and is outweighed by the benefits.
'The risk is higher the longer you take it, and the risk is higher with combined HRT compared to oestrogen-only HRT.
'Taking HRT is a very personal decision and, as such, it's vital that everyone has the information they need on the benefits and risks, discusses them with their GP or specialist team and is supported to make the choice that's right for them.'
Separate research has previously linked HRT tablets—which are less commonly used in the UK—with an increased risk of blood clots and strokes.
One in seven women in the UK are diagnosed with breast cancer in their lifetime around 56,000 a year—making it the most common cancer in the UK.
The figure stands at roughly 300,000 annually in the US. Around 85 per cent of women diagnosed with breast cancer survive more than five years.
Earlier this year, however, a shock NHS survey found women are avoiding mammograms because they are worried about being topless, think it will hurt, or haven't found a lump.
Figures show that currently a third of women asked for screening do not attend. That rises to almost half of women who are invited for the first time.
