Management of disappearing lesions after chemotherapy for colorectal liver metastases: Relation between detectability and residual tumors

Background and Objectives To clarify the detectability of gadolinium ethoxybenzyl diethylene-triamine pantaacetic acid enhanced magnetic resonance imaging (EOB-MRI) and contrast-enhanced intraoperative-ultrasonography (CE-IOUS) for residual disease in disappearing colorectal liver metastases (DLMs) and to seek a better management for DLMs. Methods Eighty-two patients who underwent hepatectomy after chemotherapy for colorectal liver metastases were retrospectively reviewed. Lesions which disappear on post-chemotherapy contrast-enhance CT were defined as DLMs. All the patients underwent EOB-MRI and CE-IOUS. With pathologic evaluation for resected specimens and clinical observation of anatomically corresponding site for non-resected lesions, detectability of residual disease in DLMs were estimated between these two imaging modalities. Results Twenty (18%) patients presented with 111 DLMs, and EOB-MRI and CE-IOUS identified 64 (57.6%) and 62 (55.9%), respectively. Residual disease was pathologically confirmed for 69.2% in resected specimens and clinically estimated in 33.3% for non-resected DLMs. EOB-MRI showed a higher accuracy of prediction of residual disease compared with CE-IOUS (0.90 vs 0.70). Of the 11 non-resected lesions which were undetected with CE-IOUS and regrew after surgery, 9 (81.8%) were detected on EOB-MRI. Conclusions EOB-MRI may be superior to CE-IOUS in detecting residual tumors for DLMs. Maximum attempt of resection would be needed for visualized lesions in EOB-MRI.