The Government has been forced to rewrite its advice on breast cancer screening after research showed that thousands of women have been misled into having unnecessary surgery.

Women invited for screening by the National Health Service will be told that some of the cancers detected will be dormant and may never spread to other tissue.

Research published this year showed that for every 2,000 women screened regularly for a decade, one life would be saved but 10 healthy women would be treated unnecessarily. The information now given to women has been criticised for advertising only the benefits and not the risks to encourage women to be screened.

Joan Austoker, author of the NHS leaflets, admitted it had been a mistake to withhold information about potentially unnecessary treatment for a type of breast cancer called ductal carcinoma in situ. Austoker, director of the primary care education research group at Oxford University, who is writing the advice by the NHS breast screening programme, said: “We want to make sure that all the risks of breast screening are referred to in appropriate detail.

“Much of the ductal carcinoma in situ diagnosed will never surface clinically. Therefore it constitutes overdiagnosis — that is, you are diagnosing something that would not have become an issue.”

Ductal carcinoma in situ accounts for 20% of the diagnoses made through screening. Less than half of the dormant cancers will progress to become invasive but 30% are treated with mastectomies. The other downsides of screening, to be described in more detail in the advice, include missing some cancers and the anxiety caused by identifying others that do not exist, so-called “false positives”.

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