The original decision to introduce mammographic screening in the UK was based on The Forrest report  which analyzed the costs and benefits of screening in terms of quality-adjusted life-years (QALYs) and found that screening would reduce the death rate from breast cancer by almost one-third with few harms and at low cost. Since that time, certain harms associated with breast screening have been identified including overdiagnosis and unnecessary surgery .
A recently published paper  set out to replicate the original Forrest report using baseline mortality and risk of surgery from English data (not originally used by Forrest) but also included the perceived harms noted above, using estimates based on those published by The Nordic Cochrane Centre  and by Nelson and colleagues [5,6] for The US Preventive Services Task Force.
The outcomes of 100,000 women aged 50 years were modelled in two cohorts, one screened, the other not. Outcomes measured were deaths from breast cancer, deaths from all other causes and the number of women having false-positive diagnoses and surgery, which were combined into QALYs. The authors found that inclusion of the effects of harms reduced the updated estimate of net cumulative QALYs gained after 20 years from 3301 to 1536 or more than 50%. Using Nordic Cochrane Centre estimates generated negative QALYs for the first 7 years of screening and only 70 positive QALYs after 10 years and 834 after 20 years. Results were similar when estimates used by Nelson were applied. Hence breast cancer screening might have caused net harm for up to 10 years from the start of screening.
Clinical Associate Professor of Obstetrics and Gynaecology, Sydney Medical School, The University of Sydney, NSW, Australia
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