Transarterial embolization for hepatocellular carcinoma: reasoning on mechanisms of action, tips and tricks of the procedure

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Transarterial embolization (TAE) and transarterial chemoembolization (TACE) are two procedures used in hepatocellular carcinoma (HCC) management. Although TAE and TACE have been compared in several studies, none of them has reported a clear clinical benefit in survival between the two techniques 1–3. To date, there is no specific drug that has proven good efficacy over HCC. This is because HCC is very chemoresistant; thus, the technical aspect of embolization seems to be the key point rather than chemotherapy. However, for maximum efficiency with TAE, it is mandatory to embolize all tumour sinusoids and the first venous outflow drainage areas (the portal venous side of the tumour) 4. Therefore, to achieve this result, it is necessary to follow some technical aspects.
The entire angiographic procedure has to be performed with iodine contrast medium at ∼37°C using an automatic warm contrast medium injector system.
Before the injection of the embolic suspension, glyceryl trinitrate has to be injected into the target feeding arteries if the HCC through the microcatheter is to achieve the maximum vascular dilatation. Then, the microcatheter should be flushed with warmed saline solution at ∼40°C to ensure a persistent and stable vasodilatation.
Injection of iodized oil (Lipiodol Ultra-Fluide; Laboratoire Guerber, Aulnay-Sous-Bois, France) into the hepatic artery started in the 1980s and it was shown to accumulate selectively into HCC with embolic effects. A recent paper has shown that warmed (40°C) emulsion of a chemotherapeutic agent and Lipiodol reduces its viscosity to half compared with the room temperature (25°C) one 5. This ensures that more than 60% of the warmed chemotherapeutic agent and Lipiodol emulsion reach tumour sinusoids and the portal venous system around the HCC (Fig. 1).
Therefore, from the 1980s to date, the use of chemotherapeutic agent and Lipiodol (conventional TACE) remains the most common transarterial technique for the treatment of HCC. However, patients with HCC often require repeated sections of transarterial treatments for residual tumour or local recurrence. It has been shown that chemotherapeutic agents lead to hepatic arterial damage, and this may interfere with catheterization for the next treatment step, with limitations in efficacy and consequently clinical outcomes 6.
From these statements, a warmed saline solution and Lipiodol emulsion at ∼40°C, followed by the use of gelatin sponge particles, could be considered a possible ideal embolic technique.

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