The diagnostic performance of mammogram (MMG) reading alone was compared with that of inspection and palpation alone using identical subjects. Both diagnostic procedures were performed independently by different physicians. This was followed by a prospective study, i. e., definitive diagnosis for each patient was made by surgery and/or biopsy etc. after MMG and inspection and palpation. Nine institutions participated in this study, involving a total of 58 physicians, producing data obtained by palpation, MMG and definitive diagnosis in 397 cases. Receiver operating characteristic analysis (ROC) based on data from definitive diagnosis suggested that MMG reading is less capable than inspection and palpation of diagnosing the presence of a mass, but is equally capable of diffrentiating breast cancer from normality and benign lesions. In cases with calcium deposits, MMG was confirmed to be even more capable of making a diagnosis than inspection and palpation. However, in order to confirm the tendency revealed by the present study, it is essential to improve the reliability of definitive diagnosis of normality/ benignity and to study a larger number of cases.

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With the aim of evaluating diagnostic performance and inter-observer variation of mammography, mammograms (MMGs) in 50 cases from the previous study were analyzed retrospectively. Without knowledge of either data from inspection and palpation diagnosis or clinical data, a study of MMGs reading by 10 physicians and 7 radiology technicians was carried out. The results showed that participating physicians and technicians, on the whole, were equally capable of detecting a mass and of differentiating breast cancer from normal cases and benign cases. In addition, variations in these capabilities among the physicians and technicians were nearly identical. Given the fact that the technicians engaged in the present study were specialists in mammography, these results suggest that technicians in general have the potential of reaching the same level of diagnostic performance as that of physicians if they are given suitable education and training, and that it is possible to establish a MMG reading system in which radiology technicians perform the MMG reading in the mass screening of breast cancer. Under these circumstances, the present results also suggest that it is urgently necessary to establish a mammographic technique for mass screening that is acceptable to the majority of MMG readers at other institutions.

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