The report, commissioned by Cancer Research UK and the Department of Health (England), reviews the benefits and harms of breast cancer screening in the UK. The primary benefit of screening is a reduction in mortality from breast cancer, estimated at 20% based on meta-analyses of 11 randomized controlled trials with 13 years of follow-up. However, there are uncertainties in this estimate, including statistical variability and potential biases in the trials. The report also addresses the harm of overdiagnosis, where cancers detected by screening would not have become clinically apparent otherwise. Overdiagnosis rates are estimated to be around 11% from a population perspective and 19% from a woman's lifetime perspective. The panel concludes that the UK breast screening programs, which invite women aged 50-70 every 3 years, provide significant benefits by preventing about 1300 breast cancer deaths annually. However, these benefits must be balanced against the harms of overdiagnosis, which can lead to unnecessary treatment and psychological distress. The panel recommends that the programs continue, emphasizing clear communication of the risks and benefits to women.The report, commissioned by Cancer Research UK and the Department of Health (England), reviews the benefits and harms of breast cancer screening in the UK. The primary benefit of screening is a reduction in mortality from breast cancer, estimated at 20% based on meta-analyses of 11 randomized controlled trials with 13 years of follow-up. However, there are uncertainties in this estimate, including statistical variability and potential biases in the trials. The report also addresses the harm of overdiagnosis, where cancers detected by screening would not have become clinically apparent otherwise. Overdiagnosis rates are estimated to be around 11% from a population perspective and 19% from a woman's lifetime perspective. The panel concludes that the UK breast screening programs, which invite women aged 50-70 every 3 years, provide significant benefits by preventing about 1300 breast cancer deaths annually. However, these benefits must be balanced against the harms of overdiagnosis, which can lead to unnecessary treatment and psychological distress. The panel recommends that the programs continue, emphasizing clear communication of the risks and benefits to women.