Breast screening risks and benefits “For every life saved by
breast cancer screening up to 10 women ‘have unnecessary
treatment’,” the Daily Mail reported today. The news is based on
a study that looked at the impact of screening in Norway, and
how often it led to “overdiagnosis”. Overdiagnosis is the
phenomenon where women are correctly diagnosed but given
treatment even though it will not improve their survival. This
could be because the tumour identified would not have progressed
to a clinical stage (would never have caused symptoms) or
because the woman would have died from another cause, such as
old age, before the cancer reached a clinical stage. Using
nearly 20 years of data, researchers estimated that Norway’s
screening programme had an overdiagnosis rate of 15–25%. This
equated to 6 to 10 women being overdiagnosed for every 2,500
women invited for screening. In comparison, 20 in 2,500 women
screened were diagnosed with breast cancer that was not
overdiagnosed. Screening 2,500 women was estimated to p