Role of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography in Detection of Portal Vein Tumor Thrombosis in Hepatocellular Carcinoma

Abstract

A 56 year old gentleman with no known comorbidities presented with pain abdomen for 1 month. Triphasic CECT abdomen showed features of cirrhosis with surface irregularities, fissural widening and volume redistribution changes in the liver. Segment VII of liver showed an arterial enhancing lesion measuring 4.2 x 3.5cm showing washout in delayed phase. In view of BCLC A stage with Child Pugh B7, ablation was planned. Before proceeding with ablation, in view of very high alpha-fetoprotein (AFP) level of 9836 ng/mL, he was advised for metastatic evaluation with 18F-FDG PET-CT. The PET scan showed abnormal heterogeneous increased FDG uptake in segment VII of liver (SUV Max 4.7) with arterial enhancement and washout suggestive of metabolically active hepatocellular carcinoma. Also seen was an abnormal linear increased FDG uptake in right branch of portal vein (SUV Max 4.8) which was suggestive of portal vein invasion. In view of portal vein tumor thrombus, ablation procedure was deferred for the patient. Role of PET scan in HCC with vascular invasion is not yet defined. Poor specificity of FDG PET is the major hindrance in establishing PET scan as diagnostic tool for vascular invasion. In small segment invasion when CECT is not able to differentiate between tumour versus bland thrombus PET scan may be significant tool to differentiate between bland thrombus and tumour thrombus. Vascular invasion confirmation have treatment related and prognostic significance. There is a need for a prospective study evaluating the prognostic significance of PET scan based diagnosis of vascular invasion.