In 2002, the Women's Health Initiative (WHI) study was terminated early after oestrogen plus progesterone HRT was found to be linked to a 26 per cent increased risk of breast cancer and a 29 per cent higher risk of heart attack.
Subsequently, women have been advised to take HRT for as short a time as possible. But follow-up data from the WHI suggests that the increased cancer risk remains after stopping HRT.
The latest data comes from follow-up of 15,730 postmenopausal women, aged 50-79, who had participated in the WHI study. Half the women had been taking oestrogen plus progesterone HRT, but stopped the treatment in 2002 when the WHI study was abandoned. The rest of the women had taken placebo.
Follow-up from July 2002 until March 2005 revealed that 281 women who had received HRT went on to develop cancer, compared with 218 who had not received HRT.
Overall, the combined risk of suffering heart disease, stroke, hip fracture or cancer was 12 per cent higher in the HRT group than the placebo group.
Researchers from the University of North Carolina hope the findings can help calculate the optional use of HRT.
Dr Kat Arney, Cancer Research UK's senior information officer, said: 'This significant study adds to the evidence that women should only take HRT specifically to treat symptoms of the menopause, and for as short a time as possible.
'Women who are taking HRT and are concerned about their risk of cancer should speak to their doctor.'
JAMA 2008; 299: 1,036-45
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