Our experts respond to new study about continuing breast cancer risks after HRT

A study has found the risk of breast cancer when using hormone replacement therapy (HRT) is higher than previously thought and continues when HRT is stopped, prompting new information from the Medicines and Healthcare Products Regulatory Authority (MHRA). However, our experts say that HRT still has an important role to play in osteoporosis care.

The study, published in The Lancet, looked at data from nearly 570,000 postmenopausal women in 58 studies, and compared the risk of breast cancer among those who took HRT and those who did not.

No great risk was found in those women using HRT for less than one year. However, those using HRT for more than one year had an increased risk of developing breast cancer, and their risk increased further the longer HRT was used. Women appeared to remain at an increased risk for 10 or more years after stopping treatment.

HRT replaces sex hormones, particularly oestrogen, that are at a lower level after the menopause. It is commonly taken to help relieve symptoms of the menopause, such as hot flushes and night sweats, but can also be prescribed for osteoporosis to help strengthen bones.

Most women who take HRT for their bones are prescribed combined HRT (containing both oestrogen and progestogen), because oestrogen-only HRT slightly increases the risk of womb cancer.

It’s long been recognised that combined HRT increases the risk of developing breast cancer, but this research gives us more information about these risks.

In the UK, about one in 16 women aged 50 to 69 develop breast cancer without ever having taken HRT (equal to 63 cases of breast cancer per 1,000 women). The study estimated that, over the same period (aged 50 to 69):

• Five years’ use of oestrogen-only HRT would cause an extra five cases of breast cancer per 1,000 women
• Five years' use of combined HRT (containing both oestrogen and progestogen) for part of each month (known as sequential HRT) would cause an extra 14 cases per 1,000 women
• Five years' use of combined HRT (containing both oestrogen and progestogen) daily (known as continuous HRT) would cause an extra 20 cases per 1,000 women

Our experts reiterate that HRT still has an important place in osteoporosis care and is an appropriate treatment for some women with the condition – particularly those who have had an early menopause – but that treatment decisions for women should be made on an individual basis, depending on their medical history and risk factors.

Juliet Compston, our clinical adviser and Emeritus Professor of Bone Medicine at the University of Cambridge, says: “HRT continues to be a treatment option for osteoporosis in women aged 60 years or below who are at high risk of breaking a bone and also have troubling menopausal symptoms.

“However, the study does provide additional information about how breast cancer risks don’t disappear when HRT is stopped and clear figures for the increase in absolute risk during and after HRT.

“These need to be taken into consideration and should be included in discussion between healthcare professionals and patients when making decisions about starting HRT.”

Our HRT fact sheet is being updated to reflect these changes. Until then, if you have a question about HRT for osteoporosis or bone health, you can contact our specialist nurses on 0808 800 0035 or email nurses@theros.org.uk.

Find out more about HRT and osteoporosis.