Breast cancer screening may lead to less overdiagnosis than previously thought

A new study sheds light on a longstanding debate over how frequently breast cancer screenings detect cancers that would never have caused health problems. Known as overdiagnosis, this can lead to unnecessary treatment. Researchers at the University of Southern Denmark analyzed data from previous randomized mammography trials and compared the findings with long-term screening data. They concluded that fewer than 5% of breast cancers detected through screening may represent overdiagnosis, substantially below earlier estimates of 30% to 50%. The researchers said those higher estimates may have resulted from limited follow-up and other methodological issues.