A new meta-analysis of more than 100,000 women with breast cancer published in The Lancet has shown that the increased risk of breast cancer associated with systemic HRT lasts more than 10 years after stopping treatment.
'There is no need for urgent action but women who use, or are planning to use, HRT should be aware of these new findings when considering their HRT use at their next routine appointment,' said the MHRA.
The meta-analysis examined participant data from the Collaborative Group on Hormonal Factors in Breast Cancer comprising 108,647 cases of breast cancer documented in prospective studies. The analysis included long-term follow-up of women who did not use HRT and those who discontinued HRT, mostly in the early 2000s. Among women with complete information, mean HRT duration was 10 years in current users and 7 years in past users.
Systemic HRT is known to be associated with a significant excess incidence of breast cancer and the risk is higher for combined oestrogen-progestogen HRT than oestrogen-only HRT.
The analysis found there is little or no increase in risk with current or previous use of HRT for less than 1 year; however, there is an increased risk if it is used for longer than 1 year and the risk increases further with the duration of HRT use.
The risk decreases after stopping HRT, but remains elevated for more than 10 years in ex-HRT users compared with women who have never used HRT.
In the UK about 1 in 16 never-users of HRT (about 63 per 1000) will be diagnosed with breast cancer between the ages of 50 and 69 years.
Among women of average weight who start using systemic HRT from menopause in their 40s or 50s, and continue for 5 years, the extra number of cases of breast cancer by age 69 years is estimated from the analysis to be:
- around 1 extra case per 200 women (corresponding to about 5 extra cases per 1000 women) who use oestrogen-only HRT
- around 1 extra case per 70 women (corresponding to about 14 extra cases per 1000 women) who use oestrogen combined with progestogen for part of each month (sequential or cyclical HRT)
- around 1 extra case per 50 women (corresponding to about 20 extra cases per 1000 women) who use oestrogen combined with daily progestogen HRT (continuous HRT)
The number of extra cases up to age 69 years is approximately double these values for women who use systemic HRT for 10 years compared with those who use HRT for 5 years.
The increased risk of breast cancer was seen with all forms of systemic HRT, irrespective of the type of oestrogen or progestogen or route of delivery (oral or transdermal). Consistent with previous studies, the analysis found no evidence of an effect on breast cancer risk with use of low doses of oestrogen applied directly via the vagina to treat local symptoms.
Prescribers of HRT should inform women who use or are considering starting HRT of the new information about breast cancer risk at their next routine appointment. The MHRA has produced an information sheet for women to aid these discussions. This sheet can be used by healthcare professionals alongside a new table summarising risk estimates for breast cancer and other conditions based on 5 years' and 10 years' use of HRT.
Commenting on the meta-analysis, Sarah Branch, Deputy Director of MHRA’s Vigilance and Risk Management of Medicines (VRMM) Division, said: '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.
'No medicine is completely without risk, but it is important for women to be able to make an informed decision about the risks and benefits that are appropriate for them.'
HRT should only be prescribed to relieve post-menopausal symptoms that are adversely affecting quality of life and regular reviews are recommended for women using HRT to ensure it is used for the shortest time and at the lowest dose.
Healthcare professionals should remind current and past HRT users to be vigilant for signs of breast cancer and encourage them to attend for breast screening when invited.