by Stephen W. Duffy, MSc, Wolfson Institute of Preventive Medicine, Queen Mary University of London
Since the 1960’s, hundreds of thousands of women have been enrolled in randomised controlled trials of breast cancer screening using mammography. It would be difficult to find a medical procedure which has undergone such extensive testing and scrutiny. The randomised trials show a significant reduction in breast cancer mortality, of the order of 20%, with invitation to screening. Since not all women invited to screening actually attend, it has been estimated that the effect of actually being screened is to reduce breast cancer mortality by 30-40%.