Screening could over diagnose breast cancer

Reported by Susan Aldridge, PhD, medical journalist

Analysis of data from a screening trial suggests that there is a ten per cent of overdiagnosis of breast cancer.
The benefit of breast screening for reducing deaths from breast cancer is now well established. However, a team at Malmo University Hospital in Sweden now warns that breast cancer can be over-diagnosed with screening.

Over-diagnosis is defined as cases of cancer that would not have come to light - or caused any problem - were it not for screening. The researchers looked at data from a large breast screening trial conducted in Sweden between 1976 and 1986 and followed up the trial participants to 2001. Those in the trial were compared with an unscreened control group. This revealed an over-diagnosis rate of ten per cent. Other studies have suggested different rates of over-diagnosis but were not based upon direct observation like this one. Clearly over-diagnosis is an unwelcome side effect of screening, leading to unnecessary treatment and anxiety. But it must be set against the undoubted benefits of having a screening program.

Source
BMJ Online First 2nd March 2006

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