F-18 FDG PET in the Evaluation of Hepatocellular Cancer
Dear OncoLink "Ask The Experts,"
Peeyush Bhargava, MD, Chief Fellow in the Department of Nuclear Medicine at the University of Pennsylvania, responds:
PET scans using FDG have been shown to be of limited value in the diagnosis and initial evaluation of patients with hepatocellular cancer lesions in the liver. Hepatocellular cancers show variable degree of FDG uptake, which can be higher, equal to, or lower than liver background. This can make it very difficult to interpret the PET scan results. However, there are individual settings where PET appears to be useful.
Whole body PET imaging can be very useful for: initial evaluation of undiagnosed liver tumors or masses (differentiation between benign and malignant liver neoplasms); the detection of unsuspected metastasis from hepatomas (as only the patients with small tumors (<5 cm) and no distant metastasis, benefit from surgery); evaluation and treatment monitoring of hepatic metastasis (from colon, pancreatic, lung and breast cancers); monitoring response to therapy (chemo-embolisation and radiofrequency ablation) in patients with hepatocellular cancer. PET may also have a prognostic value in patients with hepatomas as there is a correlation between the degree of FDG uptake and the degree of malignancy and in turn patient survival.
Below are the whole body FDG PET anterior projection images of a 64 year old male with history of hepatocellular cancer. Image "A" shows a large circular area of intense FDG activity in the right lobe of liver consistent with primary hepatocellular cancer (red arrow). The finding was confirmed on the MRI and the mass was biopsied. No metastatic lesions were seen. The green arrow points to the normal heart muscle activity, the blue arrow to the normal bladder activity and the brown arrow to the activity in the back muscles. The tumor was treated with chemo-embolization and radiofrequency ablation (RFA). The post therapy MRI did not show any change in the characteristics of the mass, but the follow-up PET (image "B") showed significant reduction in the metabolic activity of the mass (red arrow) and the presence of metastasis in the lungs (small red arrows), which were confirmed to be enlarging lung nodules on the follow-up CT scan.