British Society of Breast Radiology Annual Scientific Meeting 2016: Manchester, UK. 6-8 November 2016

Jennifer Ferguson2, Guy Stevens1, Robert Hills2, Kate Gower Thomas1 1Breast Test Wales, Cardiff, UK; 2Cardiff University School of Medicine, Cardiff, UK Correspondence: Jennifer Ferguson Introduction To determine the rate and classification of interval breast cancer (IC) in the two years preceeding and following the introduction of digital mammography in 2011 in a national screening programme. Methods Two 2-year bands were used to ensure completed data for pre and post digital groups. Retrospective analysis of a prospectively collected database of IC was undertaken, identifying women who had undergone screening in the two years prior to and after the introduction of digital screening mammography (1.1.10 until 31.12.11 and 1.1.12 until 31.12.13). Chi squared analysis was used to compare the rate between the two groups and the rate of false negative (FN) and minimal signs (MS) categories considered together. Results Of 87,868 screened before digital between 1.1.10 and 31.12.11, 103 developed IC (0.12%) and of 100,672 screened with digital between 1.1.12 and 31.12.13, 145 developed IC (0.14%) (p = 0.12). Those women with FN and MS interval cancer numbered 17 (16.5%) predigital and 41 (28.3%) with digital; (p = 0.04). The number of true IC was similar in the pre (49.5%) and post (46.9%) groups. Conclusion The rate if IC is similar to the NHSBSP standard (1.2 per 1000 women screened). Despite earlier groups indicating that digital technology will lessen the number of IC, especially those ‘missed’ (FN and MS groups) which are often asymmetric densities and poorly defined masses, this has not been found in our study. The reasons for this will be discussed and examples will be shown.