Purpose: To compare the prognostic implications and positron emission tomography (PET)/computed tomography (CT) characteristics of isolated bone metastasis secondary to hepatocellular carcinoma (HCC) with those of HCC metastases to bone and other sites. Materials and Methods: This study was approved by the institutional ethics committee, and informed consent was obtained from all patients. Extrahepatic metastases were diagnosed in 257 patients with HCC by using dual-tracer (carbon 11 [C-11] acetate and fluorine 18 fluorodeoxyglucose [FDG]) PET/CT. Metastatic bone lesions were identified with visual inspection and semiquantitative assessment and confirmed with histopathologic examination and/or supported by findings at other radiologic examinations or serial PET/CT. Results: The frequency of bone metastasis from HCC was 19% (49 of 257 patients; eight patients had histopathologic proof and 41 had imaging proof). Metastasis isolated to bone (group 1, 30 of 257 patients [12%]) was more common than metastasis to bone and other sites (group 2, 19 of 257 patients [7%]). At lesion-based analysis of group 1 (71 index lesions; mean lesion size +/- standard deviation, 3.25 cm +/- 1.88), C-11 acetate PET was more sensitive than FDG PET (93% [66 of 71 lesions] vs 62% [44 of 71 lesions], respectively; P < .05). The combined sensitivity was 97% (69 of 71 lesions) with dual-tracer PET and 72% (51 of 71 lesions) with CT. At patient-based analysis, C-11 acetate PET had an incremental value of 23% (seven of 30 patients) over FDG PET. At lesion-based analysis of group 2, FDG PET was more sensitive than C-11 acetate PET (87% [33 of 38 lesions] vs 50% [19 of 38 lesions], respectively; P < .05). Tracer avidities of metastatic bone lesions were closely correlated with that of their corresponding primary HCC tumors. The median survival time was longer in group 1 than in group 2 (18 months vs 11 months, respectively; P < .05). Conclusion: Isolated bone metastasis from HCC may not be as uncommon as previously believed. The detection of these metastases can be significantly enhanced with C-11 acetate PET compared with FDG PET alone. Identification of this group of patients also seems to have prognostic importance. (C)RSNA, 2010
