CADET II: A prospective trial of computer-aided detection (CAD) in the UK Breast Screening Programme

Abstract

508 Background: Computer-aided detection (CAD) systems that attract the reader's attention to potentially suspicious features on a mammogram are now in clinical use in screening mammography in the USA. Double reading increases small cancer detection by up to 10%, and the aim of this trial was to evaluate whether the performance of a single reader using CAD can match that of standard double reading in the UK Breast Screening Programme. Methods: Information about the study was posted to women invited for routine screening mammography at three UK screening centers. Informed consent was obtained at the time of the mammography appointment. Film batches were randomly assigned in a ratio of 28:1:1 to one of three film reading regimes: mammograms double read and single read with CAD, mammograms double read only, mammograms single read with CAD only. Double reading was conducted according to standard protocol. For single reading with CAD, mammograms were digitized and analyzed by an ImageChecker CAD system V8.1 and readers viewed the CAD prompted images on a low resolution computer display screen or hard copy printouts. The study was designed as a prospective multicenter randomized trial with matched comparison of single reading with CAD and double reading in terms of the number of women recalled for assessment, cancer detection rate and staging of the two reading regimes. Equivalence was defined as a 95% confidence interval on the difference between cancer detection rates of no more than 10% in either direction and the estimated sample size was 30,000 women. Results: 31,293 women were recruited into the trial between September 2006 and August 2007. The cancer detection rates of the two reading regimes were comparable (86.5% for single reading with CAD and 87.8% for double reading). This equates to a difference of −1.3% (95%CI −8.4%, +5.7%; p=0.7). Recall rates were 3.9% for single reading with CAD and 3.3% for double reading, a small but significant, absolute difference of 0.6% (95%CI 0.3%, 0.8%; p<0.007), a relative difference of 18%. Conclusions: The cancer detection rate of single reading with CAD was comparable to that achieved by double reading with only a small increase in recall rate. The results of this study should inform policy on the potential of CAD to improve efficiency in the UK Breast Screening Programme. No significant financial relationships to disclose.