Danish researchers are claiming that the benefits of breast cancer screening are questionable and that mammograms can lead to women being given unnecessary and harmful treatment.
Researchers at the Nordic Cochrane Centre in Denmark suggest that women should be better informed of the harms of breast cancer screening, including the increased likelihood of having a mastectomy and receiving radiotherapy.
The researchers reviewed breast cancer research papers from around the world and studied both the benefits and negative effects of seven breast screening programmes on 500,000 women in Canada, the U.S., Scotland and Sweden.
They found that for every 2,000 women invited to have mammograms over a 10-year period, one would have their life prolonged but 10 would endure potentially devastating and unnecessary treatment.
They also revealed a further 200 women out of every 2,000 experienced distress and anxiety because of false positives - a result that indicated a cancer was present but was later found to be wrong.
They say that while overall screening has reduced mortality by about 15 per cent, it has also increased the number of mastectomies by 20 percent and the likelihood of radiotherapy.
They found that though mammograms did reduce the number of women dying from the disease, the screening was diagnosing woman with breast cancer who would have survived without treatment, meaning they were undergoing unnecessary chemotherapy, radiotherapy or mastectomies.
A fifth of cancers picked up by screening are found in the milk ducts of the breast, some of these cancers will progress while others will not, but there is no way of predicting what will happen.
Breast screening programmes in the UK provide free breast screening for women over 50 every three years, and they have questioned the research.
The Department of Health's advisory committee on breast cancer screening which carried out a comprehensive evaluation of the programme, found that for every 2,000 women joining it over 10 years, five lives would be prolonged.
The NHS says that breast screening saves 1, 400 lives each year and that women who were screened were less likely to have a mastectomy than those who were not screened and the benefits of breast screening far outweigh the risks.
Dr Peter Gotzsche, the director of the Nordic Cochrane Centre has described the NHS statement that screening led to a reduction in the number of mastectomies as "misleading".
Another expert Professor Michael Baum, a long-term critic of screening, has called on the NHS programme to be independently assessed by the National Institute for Clinical Excellence, in the same way that the breast cancer drugs arimidex and herceptin were.
In 2001, the same authors concluded there was no convincing evidence that screening programmes reduce mortality from the disease.
The report is published in the Cochrane Library.