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Importance of Comparison of Current and Prior Mammograms in Breast Cancer Screening¹

Antonius A. J. Roelofs, PhD, Nico Karssemeijer, PhD, Nora Wedekind, MS, Christian Beck, PhD, Sander van Woudenberg, MS, Peter R. Snoeren, PhD, Jan H. C. L. Hendriks, MD, Marco Rosselli del Turco, MD, Nils Bjurstam, MD, Hans Junkermann, MD, David Beijerinck, MD, Brigitte Séradour, MD and Carl J. G. Evertsz, PhD

¹ From the Department of Radiology, Radboud University Nijmegen Medical Center, Geert Grooteplein 10, 667 Radiology, 6500 HB Nijmegen, the Netherlands. From the 2004 RSNA Annual Meeting. Received April 25, 2005; revision requested June 21; revision received November 21; accepted December 15; final version accepted April 10, 2006. Supported by a grant from the European Community in the 5th Framework Information Society Technologies program (IST-2001-33439, SCREEN-TRIAL). Address correspondence to A.A.J.R. (e-mail: T.Roelofs{at}rad.umcn.nl).

Purpose: To retrospectively determine the influence of comparing current mammograms with prior mammograms on breast cancer detection in screening and to investigate a protocol in which prior mammograms are viewed only when necessary.

Materials and Methods: Institutional review board approval was not required. Participants gave written informed consent. Twelve experienced screening radiologists read 160 soft-copy screening mammograms twice, once with and once without prior mammograms. Eighty mammograms were obtained in women in whom breast cancer was diagnosed later; the other 80 mammograms had been reported as normal or benign. All cancers were visible in retrospect. Readers located potential abnormalities, estimated likelihood of malignancy for each finding, and indicated whether prior mammograms were considered necessary. The effect of prior mammograms on detection was determined by computing the mean lesion localized fraction in a range of low fractions of nonlesion locations corresponding to operating points in screening. Scores for both reading sessions were combined to assess the effect of making prior mammograms available only when requested. Data were analyzed by comparing the number of localized lesions between the two reading conditions with a paired two-tailed Student t test and applying a linear mixed model to test differences in average mean lesion localized fraction between reading conditions. P values less than .05 indicated statistical significance.

Results: Without prior mammograms, significantly more annotations were made. When only positive cases were considered, no difference was observed. Reading performance was significantly better when prior screening mammograms were available. At fixed lesion localized fraction, nonlesion localized fraction was reduced by 44% (P < .001) on average when prior mammograms were read. Performance was also increased for combined reading mode (ie, when prior mammograms were available on request only). However, this increase was smaller than that when prior mammograms were always available. Prior mammograms were requested in 24%–33% of all cases and were requested more often in positive cases.

Conclusion: Comparison with prior mammograms significantly improves overall performance and can reduce referrals due to nonlesion locations. Limiting the availability of prior mammograms to cases selected by the reader reduces the beneficial effect of prior mammograms.

© RSNA, 2007