A £20m international investigation into the risks and benefits of hormone replacement therapies was abandoned yesterday in another big setback to the HRT industry.
The decision to end the planned 13-year trials, which had recruited more than 5,000 British volunteers over the past three years, was made because they were taking too long and would not influence prescribing practice.
There is growing scientific evidence that excessive claims might have been made for the drugs used by millions of women to counter the effects of the menopause, although there is no question over their overall safety record.
The government-funded medical research council (MRC) changed its mind on the studies, for which half the money has been spent, three months after scientists on the project's steering committee recommended they should continue until 2012.
This followed publication of US research reporting small increases in the number of women developing breast cancer, heart disease, blood clots and strokes, findings which led to the American trials being abandoned.
The reason given then was that there were still unanswered questions over HRT use over a long period, including its impact on quality of life. But the MRC also asked independent advisers to review international evidence to help determine the future of Wisdom, the Women's International Study of Long Duration Oestrogen After Menopause, which was meant eventually to involve 16,000 British women and 6,000 from Australia and New Zealand.
Ray Fitzpatrick, director of the Institute of Health Sciences, at Oxford University, who chaired the advisers' committee, said: "There is strong evidence that taking HRT long-term increases the risk of diseases such as breast cancer and decreases the risks of others such as osteoporosis. However, there is no trial evidence that HRT protects women from cardiovascular disease and it may even increase their risk in the short term.
"These findings have already influenced practice in the US. The committee was concerned by the slow progress of Wisdom and considered the results of the trial, which would not be available for another decade, would be unlikely to affect clinical practice."
The MRC yesterday made clear the study was being aban doned for scientific and practical reasons, not on safety grounds.
Janet Derbyshire, director of its clinical trials unit, said: "We are naturally very disappointed when a study is stopped early. However, it is the very nature of science that new evidence emerges all the time."
The government is review-ing its advice to HRT manufacturers and patients in the wake of the US trial results. It significantly changed its guidance available through NHS Direct shortly before that because of the emerging international evidence over HRT, for which 6m prescriptions a year are issued in England alone.
Safety advisers to the government's medicines control agency insisted previous suggestions that HRT might reduce heart disease must be replaced by warnings that HRT "has not been shown to prevent heart disease". There must also be clearer information on the increased risk of breast cancer.
A spokesman for Wyeth, one of the main HRT manufacturers, said: "With all products there are risks and benefits; the main thing is doctors and their patients will decide whether HRT is appropriate for a woman on the basis of her medical history and current health care needs."
