Percutaneous ablation for perivascular hepatocellular carcinoma: Refining the current status based on emerging evidence and future perspectives

Abstract

Various therapeutic modalities including radiofrequency ablation, cryoablation, microwave ablation, and irreversible electroporation have attracted attention as energy sources for effective locoregional treatment of hepatocellular carcinoma (HCC); these are accepted non-surgical treatments that provide excellent local tumor control and favorable survival. However, in contrast to surgery, tumor location is a crucial factor in the outcomes of locoregional treatment because such treatment is mainly performed using a percutaneous approach for minimal invasiveness; accordingly, it has a limited range of ablation volume. When the index tumor is near large blood vessels, the blood flow drags thermal energy away from the targeted tissue, resulting in reduced ablation volume through a so-called "heat-sink effect". This modifies the size and shape of the ablation zone considerably. In addition, serious complications including infarction or aggressive tumor recurrence can be observed during follow-up after ablation for perivascular tumors by mechanical or thermal damage. Therefore, perivascular locations of HCC adjacent to large intrahepatic vessels can affect post-treatment outcomes. In this review, we primarily focus on physical properties of perivascular tumor location, characteristics of perivascular HCC, potential complications, and clinical outcomes after various locoregional treatments; moreover, we discuss the current status and future perspectives regarding percutaneous ablation for perivascular HCC.

Keywords: Cryoablation; Hepatocellular carcinoma; Irreversible electroporation; Liver; Microwave ablation; Perivascular; Radiofrequency ablation.

Figure 1

Images demonstrating aggressive intrasegmental recurrence after radiofrequency ablation for perivascular hepatocellular carcinoma. A: Axial computed tomography image obtained during hepatic arterial phase shows viable hepatocellular carcinoma (HCC) within the partially lipiodolized nodule (asterisk) in segment V before radiofrequency (RF) ablation. The index tumor is in contact with the right portal vein (black arrow); B: On planning ultrasonography (US), using fusion imaging with color Doppler US and magnetic resonance imaging (MRI), the low echogenic incident tumor (asterisk) is in contact with a right portal vein (black arrow); C: During RF ablation with the US fusion system, the ablation zone (A) is covered with viable enhancing tumor foci, indicating T marker on real time US/fused MR image; D: MRI scan obtained during the hepatic arterial phase 9 mo after RF ablation shows multiple small arterial enhancing nodules (white arrows) of consistent size, representing recurrent tumors. These recurrent tumors developed simultaneously in a peripheral area of the treated segment, fed by the previous peritumoral portal vein; E: The patient underwent transarterial chemoembolization for tumor control considering tumor multiplicity. Multiple small nodular tumors were detected along the portal tract on hepatic angiogram.

Figure 2

Images showing subsegmental hepatic infarction after radiofrequency ablation for perivascular hepatocellular carcinoma. A: Axial computed tomography image obtained during equilibrium phase shows 1.3-cm hepatocellular carcinoma (asterisk) in segment V before radiofrequency (RF) ablation. The index tumor is in contact with the right portal vein (black arrow); B: Planning ultrasound image obtained before RF ablation shows the low-echoic-index tumor (asterisk) in contact with a right portal vein (black arrow); C: During RF ablation, the RF electrode (white arrow) is inserted into the index tumor (asterisk), evading the adjacent portal vein; D: At the end of the procedure, a hyperechoic ablation zone (A) completely covered the index tumor; E: Thrombosis within the peritumoral portal vein (black arrow) developed around the index tumor (dotted line), shown on coronal computed tomography images obtained immediately after RF ablation. This led to subsegmental infarction (I) in the peripheral area of hepatic segment VI.