A major risk of breast cancer screening may have been overestimated for decades

A new study suggests that the risk of overdiagnosis, a potential drawback of breast cancer screening, may have been overstated for decades. Overdiagnosis occurs when screening detects breast cancers that would never have caused symptoms or posed a threat during a woman's lifetime. For years, researchers have debated the extent of this phenomenon, with estimates varying widely. The latest analysis, however, indicates that the actual rate of overdiagnosis could be far lower than previously thought.

The researchers, led by Sisse Helle Njor from the University of Southern Denmark, reevaluated the results of all randomized controlled trials on mammography screening. They focused on three factors that can affect overdiagnosis estimates: the timing of cancer detection, the introduction of screening, and the follow-up of women in the trials. By accounting for these factors, the researchers found that overdiagnosis is likely to be less than 5%, significantly lower than earlier estimates ranging from 30-50%.

This finding is crucial for women considering breast cancer screening programs, as it reassures them that the benefits of early detection and prevention of premature death outweigh the small risk of unnecessary treatment. The study provides a more realistic interpretation of the evidence, helping inform women when they receive screening invitations.