A research project into hormone replacement therapy in Britain, worth £20m, is to continue despite the abandonment of a similar study in America after warnings about the health risks to women.
About 5,000 women have volunteered for the trial, which is investigating a combined HRT drug almost identical to the one used in the US study and an oestrogen-only therapy.
The Medical Research Council, which is leading the study, announced yesterday that two independent committees of scientists had reviewed the US results and said that as long as the women were informed of the known risks, the work should carry on.
Professor Rory Collins, chairman of one committee, the Trial Steering Group (TSG), said: "Both of these committees have recommended that the trial should continue, because there are still important questions about the balance of risks and benefits with long-term HRT that have not yet been answered."
Just under half of the women taking part in the trial are on a combined HRT pill called Prempro. The therapy was linked last week by the American study to an increased risk of breast cancer, heart attacks, strokes and blood clots.
The TSG committee concluded that the increased number of breast cancers amounted to a "relatively low risk" and there were "still questions over the size of any effects" on heart disease, stroke and other cancers.
In addition, the numbers of women who had fractures or bowel cancer were slightly lower among women taking the combined drug.
The results were given in detail in letters to the participants in the trial, which was launched in 1999 and is expected to run until 2012. By then, researchers hope to have studied 16,000 post-menopausal women aged 50 to 69 in the UK and 6,000 from Australia and New Zealand.
Only five participants are known to have dropped out as a result of last week's scare and in the letter, Professor Collins urged the women to stick with the trial. It aims to find out whether HRT, in its combined or single hormone form, lowers or increases the risks of diseases such as breast cancer, heart failure, osteoporosis and dementia.
His letter said: "We hope that you will continue taking the trial medication as it is only with the support of women like you that it will be possible to answer many questions about women's health."
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