Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness

Researchers examining the effectiveness of mammography screening determined that although the rate of detection of large tumors fell after the introduction of screening mammography, the more favorable size distribution was primarily the result of the additional detection of small tumors. Women were more likely to have breast cancer that was overdiagnosed than to have earlier detection of a tumor that was destined to become large.

 N Engl J Med