Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence

Screening Mammography and Breast-Cancer Incidence Mammography detects substantially more cases of early-stage breast cancer, but late-stage diagnoses have decreased little. This study shows that up to 31% of new breast cancers may be overdiagnosed, although it is not known which tumors may have a fatal course. There are two prerequisites for screening to reduce the rate of death from cancer. 1 , 2 First, screening must advance the time of diagnosis of cancers that are destined to cause death. Second, early treatment of these cancers must confer some advantage over treatment at clinical presentation. Screening programs that meet the first prerequisite will have a predictable effect on the stage-specific incidence of cancer. As the time of diagnosis is advanced, more cancers will be detected at an early stage and the incidence of early-stage cancer will increase. If the time of diagnosis of cancers that will progress to a . . .