While hormone replacement therapy (HRT) is not broadly linked to young-onset breast cancer, using certain types before menopause could increase the risk of it developing in young women, a new study suggests.
An international team of researchers found that overall, the use of HRT – a treatment commonly used to alleviate menopause symptoms – was not connected to young-onset breast cancer. Then they looked at the specific type used.
Various types of HRT are available, containing different hormones, including oestrogen products, progestogen, or a combination of both.
These medicines can be taken or used in different ways and work by replacing the hormones oestrogen and progesterone, which can fall to lower levels as women approach the menopause.
The researchers found that oestrogen hormone therapy use appeared to decrease breast cancer risk, while oestrogen plus progestin therapy appeared to increase it.
Most studies examining the links between hormone therapy and breast cancer risk have been conducted in older women.
Previous work, which has focused on women who have already been through the menopause, suggests that oestrogen plus progestin hormone therapy is a risk factor for breast cancer.
But academics from the National Institute of Environmental Health Sciences in the US wanted to explore the risks among younger women on hormone therapy, who may take these drugs after gynaecological surgery or during perimenopause.
The new meta-analysis published in the journal Lancet Oncology examined data drawn from previous studies of 459,476 women aged 16 to 54 years old.
Some 2 per cent of this group (8,455) developed young-onset breast cancer, which means the disease was diagnosed before they were 55 years old.
And 15 per cent of women involved in the study reported using hormone therapy, with oestrogen plus progestin hormone therapy and oestrogen being the most common types.
They found that oestrogen hormone therapy appeared to reduce the risk of young breast cancer by 14 per cent, while oestrogen plus progestin therapy increased the risk by 10 per cent.
“Although the strength of these associations might vary by age at first use, duration of use, gynaecological surgery status, and other factors, unopposed oestrogen hormone therapy use appears to decrease breast cancer risk and oestrogen plus progestin therapy appears to increase breast cancer risk,” the authors wrote.
“The findings can be used to augment clinical recommendations for hormone therapy use in young women, for whom guidance was previously scarce.”
Commenting on the study, 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 on how HRT (hormone replacement therapy) may influence their chances of developing breast cancer before the menopause.
“It found that oestrogen-only therapy was linked to a lower risk, while combined oestrogen and progesterone therapy was associated with a small increase in risk of developing breast cancer in some women – particularly when used for more than two years or in women who hadn’t undergone surgery to remove their uterus or both ovaries.
“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.
“We’d encourage anyone with questions about HRT and their breast cancer risk to speak to their GP or to our expert nurses by calling our free, confidential Helpline on 0808 800 6000.”
