3. Transarterial chemoembolization

Transarterial chemoembolization (TACE) is the most commonly performed procedure by interventional radiologists for treatment of unresectable hepatic malignancies. Nearly half of all HCC patients receive TACE at some point in their disease course [19]. Multiple techniques have been used for TACE over the past few decades.

The theory behind TACE relies on the liver's dual blood supply as hepatic tumors derive their blood supply mainly from the hepatic artery while normal hepatic parenchyma is predominantly supplied by the portal vein. Percutaneous access to the arterial system is obtained via femoral or radial artery catheterization. Imaging is performed to assess for variant anatomy, portal vein patency, and tumoral blood supply. Angiograms were performed, however in recent years, Cone Beam Computed Tomography (CBCT) has played an important role during locoregional therapies and is recommended as standard of care during chemoembolization [20]. Once the feeding arteries to the tumor are identified, they are selectively catheterized and chemoembolization is performed. Chemoembolization can be achieved by bland embolization, conventional trans-arterial chemoembolization (cTACE) or with drug-eluting embolic transarterial chemoembolization (DEE-TACE).

cTACE consists of administering chemotherapeutic agent(s) combined with an ethiodized oil emulsion followed by an embolic agent i.e. Gelfoam, or microspheres. Historically, doxorubicin, cisplatin, and mitomycin C in combination were used for cTACE, however due to shortage of some of the drugs, the regimens changed. Neither drug alone or any combination of these agents have shown to be statistically superior [17, 18]. Currently in the United States and Europe, doxorubicin is used in the majority of cases while miriplatin and cisplatin are used in Japan [21].

Lipiodol is an ethiodized oil that is commonly used for cTACE and has been considered the standard of care. The thick consistency allows it act as an embolic agent, which travels further into the microvascular than microspheres. In addition, lipiodol is radio-opaque and it emulsifies the chemotherapeutic agents in oil droplets, which helps with drug delivery. In a meta-analysis of multiple randomized control trials, lipiodol was shown to be a safe, effective agent in the treatment of HCC [22].

Embolic microspheres loaded with doxorubicin for HCC or irinotecan for CRC are injected in the tumor feeding artery in DEE-TACE. Studies have shown slower, more sustained drug release with decreased systemic concentrations.

Bland embolization is also performed for HCC and neuroendocrine tumors. It can be accomplished either by injecting a mixture of Lipiodol and Gelfoam or with bland beads.
