Positron emission tomography (PET) using the radiopharmaceutical tracer fluorine-18 fluorocholine (FCh) can elucidate tumors based on differences in choline phospholipid metabolism between tumor and surrounding tissue. The feasibility of detecting hepatocellular carcinoma (HCC) using FCh PET has been shown despite constitutively high parenchymal choline metabolism in the liver. Since HCC frequently develops in the setting of chronic liver disease, we comparatively evaluated FCh PET/CT between cirrhotic and non-cirrhotic patients with HCC to investigate the effects of hepatic dysfunction on tumor detection and the tumor-to-background ratio (TBR) of FCh uptake. FCh PET/CT was performed prospectively in 22 consecutive patients with HCC (7 newly diagnosed, 15 previously treated). Of these 22 patients, 14 were cirrhotic and 8 non-cirrhotic. Standardized uptake value (SUV) measurements were obtained by region of interest analysis of the PET images. Tumor FCh uptake and the TBR were compared between cirrhotic and non-cirrhotic patients. Liver lesions were confirmed to be HCC by biopsy in 10 patients and by Barcelona criteria in 4 patients. There was correspondingly increased liver tumor FCh uptake in 13/14 of those patients, and iso-intense tumor FCh uptake (TBR 0.94) in one non-cirrhotic patient with newly diagnosed HCC. FCh PET/CT also showed metastatic disease without local tumor recurrence in 2 previously treated patients, and was negative in 6 treated patients without tumor recurrence by radiographic and clinical follow-up. Tumor maximum SUV ranged from 6.4 to 15.3 (mean 12.1) and liver TBR ranged from 0.94 to 2.1 (mean 1.6), with no significant differences between cirrhotic and non-cirrhotic patients (SUVmax 11.9 vs. 12.2, p = 0.83; TBR 1.71 vs. 1.51, p = 0.29). Liver parenchyma mean SUV was significantly lower in cirrhotic patients (6.4 vs. 8.7, p < 0.05). This pilot study supports the general feasibility of HCC detection by FCh PET/CT. However, a broad range of tumor FCh uptake was observed, and lower liver parenchymal uptake of FCh was noted in cirrhotic patients as compared to non-cirrhotic patients. Incorporating tissue profiling into future liver imaging trials of FCh PET may help determine the molecular basis of the observed variations in tumor and hepatic FCh uptake.
Keywords: Positron Emission Tomography; fluorocholine; hepatocellular carcinoma.