Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England

2010

Breast Cancer Screening: Lives Saved vs. Overdiagnosis

Sample size: 133065 publication 10 minutes Evidence: high

Author Information

Author(s): Stephen W Duffy, Laszlo Tabar, Anne Helene Olsen, Bedrich Vitak, Prue C Allgood, Tony H H Chen, Amy M F Yen, Robert A Smith

Primary Institution: CR-UK Centre for Epidemiology, Statistics and Mathematics, Wolfson Institute for Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London

Hypothesis

To estimate the absolute numbers of breast cancer deaths prevented and the absolute numbers of tumours overdiagnosed in mammographic screening for breast cancer at ages 50–69 years.

Conclusion

The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis.

Supporting Evidence

8.8 breast cancer deaths prevented per 1000 women screened for 20 years in the Two-County Trial.
5.7 breast cancer deaths prevented per 1000 women screened for 20 years in the UK programme.
4.3 cases overdiagnosed per 1000 women screened for 20 years in the Two-County Trial.
2.3 cases overdiagnosed per 1000 women screened for 20 years in the UK programme.
For every 2 breast cancer deaths prevented, 1 case is overdiagnosed.

Takeaway

Mammograms help save more lives from breast cancer than the number of women who are wrongly diagnosed with cancer.

Methodology

The study used Poisson regression to estimate the absolute numbers of deaths avoided and additional cases diagnosed in the study group compared with the control group.