A cancer charity today said claims that breast cancer screening does not save lives should be treated with extreme caution.

A group of Danish researchers say claims that mammography screening could reduce the risk of death by as much as a quarter are not born out.

They criticised trials conducted in Edinburgh, New York and parts of Sweden for being biased and producing unreliable results.

Dr Peter Gotzsche and Mr Ole Olsen, from the Nordic Cochrane Centre, Copenhagen, concluded in an article in the Lancet medical journal: "Screening for breast cancer with mammography is unjustified."

But Maureen Parsons, head of service development for Macmillan Cancer Relief in York, said: "The Danish researchers have reviewed existing studies and their results are open to interpretation.

"The better evidence in this country would indicate a drop in female mortality and a clear beneficial outcome in survival rates where early screening takes place.

"We would regard the Danish researchers' review with caution and at the moment continue to support the Government's mammography screening programme in this country because of evidence of beneficial outcomes."

But Mitzi Blennerhassett, who has had breast cancer and is founder and secretary of the campaigning group Cancer Action Now, said the researchers' claims deserved to be looked into.

Mitzi, a member of York Community Health Council, said: "A lot of people I know in the breast cancer world are of the same opinion that money spent on screening does save lives but could be better spent on people who have already developed cancer.

"It is a proven fact that most cases are found by women themselves. I would back the claims that it needs looking into by independent people."

In their research, Dr Gotzsche and Mr Olsen re-analysed eight previous trials and calculated the effect of screening on the breast cancer death rate for each. They found that two trials, in Canada and Sweden, which were rigorously conducted to ensure adequate randomisation and fairness, showed no significant effect.

But a spokesman at the Department of Health in London said that in 1997/98 breast screening detected almost 8,000 cancers, while there was a 14 per cent drop in female mortality between 1989 and 1998. "The NHS breast screening programme is a success and around one million women are screened each year," he said.

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