Dual-tracer PET/CT imaging in evaluation of metastatic hepatocellular carcinoma

We have reported previously that (11)C-acetate ((11)C-ACT) PET was complementary to (18)F-FDG PET in the evaluation of primary hepatocellular carcinoma (HCC) in relation to the degree of tumor cellular differentiation. In this retrospective study, our goals were to further explore the complementary role of (11)C-ACT and (18)F-FDG PET in the detection of metastatic HCC disease, to evaluate the tracer characteristics of individual organ metastasis, to identify the risk factors of metastasis, and to evaluate how these results could affect patient management.

One hundred twenty-one patients were selected for this study. All patients had undergone a "dual-tracer" PET/CT same-day protocol with (11)C-ACT PET/CT followed by (18)F-FDG PET/CT. Sets of criteria were chosen to define "metastasis" and "no metastasis" on a patient basis. The patients considered as true-positive (n = 97) were then divided into 4 groups on the basis of their primary HCC tracer avidity: (18)F-FDG-avid group, (11)C-ACT-avid group, (18)F-FDG- and (11)C-ACT-avid group, and a posttreatment group with metastasis but no baseline dual-tracer PET characterization of the primary tumor and no hepatic recurrence.

On a patient basis, dual-tracer PET/CT had a sensitivity of 98%, a specificity of 86%, a positive predictive value of 97%, a negative predictive value of 90%, and an accuracy of 96% in the detection of HCC metastasis. On a lesion basis, 273 metastatic HCC lesions considered as true-positive were detected and categorized according to the organ or site of metastasis: lymph node (abdominal and thoracic, 49%), lung (32%), bone (8%), and others (10%). The lesion-based and patient-based detection sensitivities were 60% and 64%, respectively, by (11)C-ACT and 77% and 79%, respectively, by (18)F-FDG, and they were complementary. In analyzing lesion tracer avidity, there was a positive statistical correlation between primary HCC avidity with the general tendency of metastasis. Clinically significant changes in management were found in patients with true-positive metastasis, of whom 19% were affected by (11)C-ACT PET alone. Dual-tracer PET/CT was more effective than single-tracer PET/CT in identifying candidates for curative therapy (negative predictive value of dual-tracer, (18)F-FDG, and (11)C-ACT PET/CT: 90%, 49%, and 37%, respectively).

This study confirmed that (18)F-FDG PET/CT is useful in the evaluation of HCC metastasis, although its role in the diagnosis of primary HCC is more limited. Dual-tracer PET/CT had an incremental value and complementary advantage when compared with single-tracer imaging in the evaluation of HCC metastasis.