OBJECTIVE: This study was undertaken to retrospectively assess the contribution of sonographic surveillance in the early detection of metachronous contralateral breast cancer. MATERIALS AND METHODS: We retrospectively reviewed the pathologic, mammographic, and sonographic records of 51 patients with surgically proven metachronous bilateral breast cancer in 2,498 surgically proven breast cancers during 2000-2006. We first evaluated cancer staging according to the method of detection used to identify metachronous breast cancers. The sensitivity of imaging studies to identify the lesions was also assessed. We compared cancer staging on the basis of whether the patient was included in a screened group, which was one in which a mammogram and sonogram were obtained within 12 months of the pathologic diagnosis of metachronous cancer. Within the screened group, we compared cancer staging on the basis of whether a screening sonogram was obtained within 6 months of the diagnosis of metachronous cancer. RESULTS: The staging of metachronous cancers showed no statistically significant differences related to detection method. The sensitivity of sonography was 94% and of mammography was 80% in the detection of metachronous cancers. The cancer stage in the screened group was 0 or stage I in 81% and that in the unscreened group was stage II or III in 71% (p < 0.05). Among the screened group, no significant difference was seen in staging regardless of whether a screening sonogram was obtained in the 6 months after diagnosis of metachronous cancer (p = 0.576). CONCLUSION: Sonography alone detected 14% of metachronous contralateral breast cancers. The results of this study suggest that annual additional sonography with mammography contributes to the early detection of metachronous cancers. However, sonography every 6 months is unlikely to be helpful for the early detection of metachronous cancer.
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