Differences in diagnostic impact of dual-tracer PET/computed tomography according to the extrahepatic metastatic site in patients with hepatocellular carcinoma.

Objectives: We compared the diagnostic performance of C-11 acetate and F-18 fluorodeoxyglucose (FDG) PET/computed tomography (CT) for the detection of extrahepatic metastasis in patients with hepatocellular carcinoma (HCC) and evaluated whether the improvement in the diagnostic performance of dual tracer PET/CT differs by the metastatic site.

Methods: Fifty-eight patients who had extrahepatic metastasis on either C-11 acetate or F-18 FDG PET/CT were enrolled, and 193 metastatic lesions were analyzed in this retrospective study. The metastatic lesions were categorized based on six sites of involvement. According to each involved site, the tracer avidity of the metastatic lesions was compared using the maximum standardized uptake value (SUVmax).

Results: Bone was the most frequent categorized metastatic site (44.8%), followed by lymph node (39.7%), lung (34.5%), soft tissue (27.6%), adrenal gland (6.9%), and vascular category (3.4%). C-11 acetate PET/CT showed a higher SUVmax than F-18 FDG PET/CT in metastatic bone lesions (P = 0.003). F-18 FDG uptake was significantly higher than C-11 acetate uptake in metastatic lymph node lesions (P < 0.001). The detection rate of dual tracer PET/CT was significantly higher in the metastatic lung (93.6%) and soft tissue (100%) lesions. However, the diagnostic performance of dual tracer PET/CT was limited in the metastatic bone and lymph node lesions because each tracer's detection rate was very high (bone: 94.6% in C-11 acetate, lymph node: 94.1% in F-18 FDG).

Conclusions: The tracer avidity of metastatic lesions differed according to the involved site. This difference affected the complementary role of dual tracer PET/CT in the diagnosis of extrahepatic metastases in patients with HCC.