Evaluation of Metabolic Characteristics and Viability of Lipiodolized Hepatocellular Carcinomas Using 18F-FDG PET/CT

This study aimed to evaluate the metabolic characteristics of lipiodolized hepatocellular carcinomas (HCCs) and the diagnostic accuracy of F-18-FDG PET/CT in assessing the viability of lipiodolized HCCs. Methods: Thirty-six patients (age range, 32-73 y) with 38 lipiodolized HCCs who had undergone transcatheter arterial chemoembolization (TACE) with lipiodol before F-18-FDG PET/CT (2-434 d) and 55 patients (age range, 36-77 y) with 57 treatment-naive HCCs who had not been treated with TACE were retrospectively studied. All patients underwent hepatic lobectomy or transplantation within 1 mo after PET/CT and multiphasic contrast-enhanced CT. F-18-FDG uptake by lipiodolized and naive HCCs was compared and correlated with tumor size, pathologic grade, serum alpha-fetoprotein (AFP) concentration, and time interval between TACE and PET/CT. The diagnostic accuracy of PET/CT and contrast-enhanced CT in evaluating the viability of lipiodolized HCC was compared. Results: Histologic examination showed 30 viable and 8 nonviable lipiodolized HCCs. Of the 30 viable tumors, 19 showed increased, 10 similar, and 1 decreased F-18-FDG uptake. Of the 8 nonviable HCCs, 3 showed increased and 5 decreased F-18-FDG uptake. Uptake by viable lipiodolized HCCs was correlated with tumor size (P < 0.05) but not correlated with pathologic grade, AFP concentration, or interval between TACE and PET/CT. In contrast, F-18-FDG uptake by naive HCCs was significantly correlated with tumor size and pathologic grade (P < 0.05 for each comparison). When lipiodolized HCCs with F-18-FDG uptake that was greater than or similar to that in the surrounding normal liver were considered viable, the diagnostic sensitivity of PET/CT and contrast-enhanced CT in the early postembolic period (<3 mo) was 100% and 94%, respectively, and that in the late postembolic period was 93% and 79%, respectively. The specificity of F-18-FDG PET/CT and contrast-enhanced CT was 63% and 100%, respectively, in the acute period. Three viable lipiodolized HCCs with high AFP concentration were true-positives on PET/CT but false-negatives on contrast-enhanced CT images. Conclusion: After TACE, F-18-FDG uptake in lipiodolized HCCs was not correlated with pathologic grade, in contrast to uptake in treatment-naive HCCs. F-18-FDG PET/CT showed a high diagnostic sensitivity in assessing the viability of lipiodolized HCCs, with moderate specificity. This method may be useful in determining the viability of lipiodolized HCCs in patients with increased serum AFP concentration or normal results on contrast-enhanced CT images.