Women taking HRT are being advised to discuss pros and cons of treatment at their next routine appointment after a large study reported increased risks of breast cancer that may persist after stopping the medication.
Reporting in The Lancet, researchers said the ‘robust’ results showed a greater magnitude of risk than previously realised and for those taking the HRT for years, that some risk continues once treatment ends.
While the findings do not change current guidance on HRT prescribing, GPs will need to explain the new study to women weighing up treatment decisions, the researchers said.
The study, using data from more than 100,000 postmenopausal women who developed breast cancer, reported the greatest risk associated with oestrogen plus daily progestagen. There was also an estimated extra case of breast cancer for every 50 average weight women taking the medication for five years from the age of 50.
For oestrogen plus intermittent progestagen, the risk was one in 70 and one in 200 for those taking oestrogen-only HRT preparations, the meta-analysis of patient data from 58 studies found.
After stopping taking HRT, some excess risk persisted for more than a decade depending on how long it had been used for, they said.
Some experts warned against reading too much into the results which did not contradict NICE guidelines on HRT prescribing.
For women taking HRT for less than a year, there was little ongoing risk once they stopped taking the medicine, the Lancet reported.
NICE has previously warned that GPs are unduly worried about prescribing HRT and encouraged its use for women as short-term symptom relief of menopause.
The researchers said their detailed meta-analysis brought together the worldwide evidence on studies that have looked at HRT.
Co-author Professor Valerie Beral, from the University of Oxford, said: ‘There are a number of new results but the first one that is most important, and that we have found for the first time clearly is that there is an increased risk that persists.’
She added that guidelines recommending use of HRT for symptom relief for the shortest possible time were still valid.
‘What will change is the advice that women get from their doctors about just what the risks are.’
Dr Louise Newson, GP and menopause specialist said the study did not reveal anything that was not already known.
‘GPs are really scared of HRT and I worry this will be another nail in the coffin which is wrong because women’s health is suffering.
‘This does not contradict anything in the NICE guidelines.’
Sarah Branch, deputy director of the Medicines and Healthcare products Regulatory Agency’s (MHRA) vigilance and risk management of medicines division said there was no need for urgent action but women should be aware of the findings when considering HRT use at their next routine appointment.
‘Women should be aware of this new information, so that it can be considered with the other risks and benefits of using HRT.
‘The menopause can have unpleasant side effects and HRT products can be effective in helping to ease the symptoms.’
The RCGP has said GPs should continue to prescribe until clinical guidelines recommend otherwise.
Professor Martin Marshall, vice chair of RCGP, 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.
‘We would urge patients not to panic as a result of this research, and to continue taking HRT as it has been prescribed to them – and we would urge prescribers to do so as normal, until clinical guidelines recommend otherwise.’
Risks of HRT
- For women of average weight in Western countries who have never used HRT, the average risk of developing breast cancer between the ages of 50 to 69 was about 6.3 per 100 women
- For women who use HRT the risk increases to:
- 8.3 per 100 in users of oestrogen plus daily progestagen – an absolute increase of 2 per 100
- 7.7 per 100 in users of oestrogen plus intermittent progestagen – an absolute increase of 1.4 per 100 users
- 6.8 per 100 in users of oestrogen-only – an absolute increase of 0.5 per 100 users