Breast cancer detection centers and case-control studies of the efficacy of screening

Case-control studies of screening efficacy have been proposed as a cost- and time-efficient alternative to randomized controlled trials. Possible source populations for such retrospective studies of breast cancer screening are considered, including women from (i) pre-existing randomized trials, (ii) non-experimental population-based studies and (iii) detection centers. On practical grounds women attending detection centers are seen to comprise the most readily accessible source of adequate numbers of cases and controls. Potential biases are addressed, involving incomplete case ascertainment, self-selection, and different screening recommendations. Data from the Guttman Breast Diagnostic Institute are used for illustration.