Breast cancer overdiagnosis may be below 5%, study finds

A new analysis of eight major randomized mammography trials suggests that the rate of breast cancer overdiagnosis may be below 5%, significantly lower than previous estimates of 30% to 50%. Overdiagnosis occurs when screening detects slow-growing cancers that would never have caused symptoms or threatened a patient’s life.

To reach these findings, researchers reexamined historical trial data from locations including New York, Canada, Sweden, and the United Kingdom. They used real-world data from Danish population screening programs as a benchmark to account for temporal biases that may have distorted earlier calculations.

Sisse Helle Njor, a professor at the University of Southern Denmark and Lillebælt Hospital, noted that while randomized trials have often been used to argue that overdiagnosis is a substantial problem, the study indicates that the interpretation is not as straightforward as previously believed.