In-depth Retrospective Review of Originally Negative Screening Mammograms from Women with Confirmed Breast Cancer.

Objectives: We aim to contribute to the assessment of the screening performance in Flanders (Belgium) and to identify valuable mammograms for subsequent studies and training. Materials and Methods: Initially negative prior screening mammograms (sMx) of 210 women with confirmed breast cancer detected by the Flemish screening programme between 2011-2013 were reviewed by a highly experienced radiologist. The review of the prior sMx was performed in three steps: 1) only prior mammograms available; 2) with index sMx (=subsequent positive sMx) present; 3) with index sMx and clinical information present. Results: The radiological review yielded 94 (45%) mammograms 'without suspicious lesions', 77 (37%) 'with minimal signs in at least one breast', and 39 (19%) 'with clearly visible tumours'. In univariate analyses, the reclassification of prior sMx was significantly associated with the date of the prior sMx, the need for a third reader for arbitration, image quality and the detector system used (computed radiography versus direct readout digital radiography), and it was not associated with the interval between screening rounds, age at prior sMx, breast density, or tumour characteristics (<T2 versus ≥T2, in situ versus invasive). In multivariate analyses, the date of the prior sMx (p = 0.001), need for arbitration (p = 0.001) and image quality (p < 0.001) remained significantly associated with the reclassification. Conclusion: This retrospective review reclassified 19% of the sMx as clearly visible tumours. With this, the Flemish screening programme performs in accordance with similar studies. The sMx reviewed in this study, form a valuable set of mammograms for training and further research.