RESUMO
PURPOSE: To evaluate the diagnostic accuracy of the commercial computer-aided detection CADx system for the reading of mammograms. MATERIALS AND METHODS: The study assessed the Second Look system developed and marketed by CADx Medical Systems, Montreal, Canada. The diagnostic sensitivity was evaluated by means of a retrospective study on 98 consecutive cancers detected at screening by double independent reading. The specificity and the positive predictive value (PPV) for cancer of the CADx system were prospectively evaluated on a second group of 560 consecutive mammograms of asymptomatic women not included in screening program. The radiologist who was present during the test assessed the abnormal mammographic findings by one or more of the following diagnostic procedures: physical examination, additional mammographic detail views with or without magnification, ultrasonography, ultrasound- or mammography-guided fine needle aspiration cytology, and core-biopsy. The exams first underwent conventional reading and then a second reading carried out with the aid of the CADx system. RESULTS: The overall diagnostic sensitivity of the CADx system on the 98 screening cancers was 81.6%; in particular it was 89.3% for calcifications, 83.9% for masses and only 37.5% for architectural distortion. The CADx markings for each mammography were 4.7 on average. Identification of invasive carcinoma was independent from tumour size. In the second group of 560 mammograms, the CADx system marked all cases identified as positive by conventional reading and confirmed by biopsy (7/7), but did not permit the detection of any additional cancer. The CADx markings per exam were 4.2 on average, the specificity was 13.7% and the PPV was 0.55% versus 13.7% recall rate of conventional reading. CADx reading led to a 1.96% (11/560) increase of the women necessitating further diagnostic investigation. CONCLUSIONS: The results of our study show that the diagnostic sensitivity of the CADx system is lower than that obtained by double independent reading at screening. Used in association with conventional reading of mammograms of asymptomatic women the CADx system did not increase diagnostic sensitivity.