And for every genuine case of breast cancer that mammography is picking up, three false-positives-'cancers' that aren't actually there-will also be detected.
These findings-by researchers from Oxford University-challenge the official line from the UK government's Department of Health that routine screening reduces breast cancer deaths by 20 per cent.
However, the Oxford researchers couldn't see any benefit when they compared the rate of breast cancer deaths in 1988, when the routine screening programme was introduced, to the rates today.
The false-positives all resulted in great stress and worry for the women, who also underwent further tests and treatment.
(Source: Journal of the Royal Society of Medicine, 2013; doi: 10.1177/0141076813486779).