Screen-film mammography versus full-field digital mammography in a population-based screening program: The Sogn and Fjordane study

Abstract

Studies comparing analog and digital mammography in breast cancer screening have shown conflicting results. Little is known about the use of digital photon-counting detectors. To retrospectively compare performance indicators in screen-film (SFM) and full-field digital mammography (FFDM) using a photon-counting detector in a population-based screening program. The Norwegian Social Science Data Services approved the study, which was part of the Norwegian Breast Cancer Screening Program. The program invites women aged 50–69 years to two-view mammography biannually. The study period was January 2005 to June 2006 for SFM and August 2006 to December 2007 for FFDM. Independent double reading was performed using a five-point rating scale for probability of cancer. Recalls due to abnormal mammography were retrospectively reviewed by an expert panel. Performance indicators for the two techniques were compared. Attendance rate was 83.6% (7442/8901) for SFM and 82.0% (6932/8451) for FFDM. The recall rate due to abnormal mammography, cancer detection rate and positive predictive value did not differ significantly between SFM and FFDM: recall 2.3% (174/7442) versus 2.4% (168/6932), cancer detection 0.39% (29/7442) versus 0.48% (33/6932), positive predictive value 16.7% (29/174) versus 19.6% (33/168), respectively (P>0.05 for all). The recall rate due to technically inadequate mammograms was 0.3% (19/7442) for SFM and 0.01% (1/6932) for FFDM. In the retrospective review, a significantly higher proportion of calcifications and asymmetric density were categorized as normal or definitively benign in FFDM compared with SFM. The average glandular dose was 2.17 mGy for SFM and 1.25 mGy for FFDM. Performance indicators show that FFDM using photon-counting detector is suitable for breast cancer screening. The lower radiation dose and lower recalls due to technically inadequate mammograms are of importance in mammography screening.