Transcatheter arterial chemoembolisation (TACE), also known as transarterial chemoembolisation, is a minimally-invasive method of administering chemotherapy directly to a liver tumor via a catheter under digital subtraction angiography (DSA). The chemoembolic agent may be delivered as a mixture with Lipiodol (known as conventional TACE) or as an injection of drug-eluting beads (known as DEB-TACE).
Transcatheter arterial embolization (TAE), also known as bland embolization (i.e. without a chemotherapy agent added), is an alternative treatment option, and there is evidence that its efficacy is comparable to TACE.
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History
Over 95% of the blood supply to a liver tumor is from the hepatic artery, whereas 80% of the blood supply to the normal liver parenchyma is from the portal vein 15. Therefore, embolization of the hepatic artery can be performed in order to induce tumor necrosis while preserving background liver function. The technique of using embolization in combination with local chemotherapy agents was developed in the early 1980s, and has since evolved into what is now known as "transcatheter arterial chemoembolisation" 16.
Indications
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unresectable hepatocellular carcinoma (HCC): usually Barcelona Clinic Liver Cancer (BCLC) stage B
either as palliative treatment or as a bridge to a liver transplant
may be an adjunct to radiofrequency ablation or anti-angiogenic agents
hepatic metastases: most commonly from colorectal carcinoma
intrahepatic cholangiocarcinoma 2
Contraindications
Absolute contraindications:
extensive tumor infiltration throughout the liver
large burden of extra-hepatic metastases
encephalopathy (indicating acute liver decompensation)
anaphylaxis to iodinated contrast
Relative contraindications:
hepatic or renal failure
uncorrectable coagulopathy
significant arteriovenous shunting of blood through the tumor
Procedure
Chemoembolic particles are used to occlude the hepatic arterial supply to the tumor with resultant cytotoxic necrosis. This is achieved by superselective catheterization of the tumor-feeding arteries using a microcatheter.
There is wide variability in the type of chemotherapy agent and embolization particles used, as well as the speed of injection 1. The most frequently used chemotherapy agent worldwide is doxorubicin 17. The chemotherapy agent is mixed with iodised oil, typically Lipiodol.
In conventional TACE, administration of the chemotherapy agent is followed by mechanical embolization, typically with gelfoam or PVA particles. In DEB-TACE, 100-300 micron drug-eluting beads are used instead 17.
Complications
vascular injuries: vasospasm, dissection, pseudoaneurysm, thrombosis
non-target embolization: particularly in the setting of an anatomical variant of the hepatic artery or arteriovenous shunting
post-embolization syndrome: occurs in 90% of patients
myelosuppression
infection including sepsis and hepatic abscess
Major complications are uncommon, only occurring in 5% of patients 13, and patients are usually discharged within 1-2 days.
Outcomes
TACE has been shown to have a significant survival benefit over best supportive care, as well as reducing patient symptoms and preventing tumor growth 1,2.
One key advantage is that the chemotherapy agent is targeted locally, reducing the systemic side effects of intravenous chemotherapy.
Response to treatment
Imaging is generally advised after 3-4 weeks: either a triple-phase CT, dynamic MRI, or contrast-enhanced ultrasound.
CT remains the imaging standard for evaluating treatment response. The accumulation pattern of the iodised oil (which has a distinct high attenuation appearance) and the enhancement pattern of the mass are both observed to evaluate treatment response. The greater the accumulation of iodised oil, the greater the necrosis of the tumor, and thus the greater the survival benefit. Conversely, enhancing areas within the tumor are considered to represent residual viable tumor 5.
Four types of CT imaging patterns have been described 7:
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type I
Ia: homogeneous accumulation of iodised oil within the entire tumor and in the surrounding area - this type of accumulation indicates a good response to treatment
Ib: homogeneous accumulation of iodised oil within the entire tumor without accumulation in the surrounding area
type II: irregular accumulation with filling defect(s) - this pattern represents suboptimal response
type III: faint accumulation
type IV: no accumulation
While there is no standardized method of assessing treatment response, the modified RECIST (mRECIST) criteria and the European Association for the Study of the Liver (EASL) criteria are typically used. Treatment response is classified as either complete response, partial response, stable disease, or progressive disease 14.
In the setting of a partial response, TACE may be repeated multiple times, but should ultimately be ceased if there is "untreatable progression", which is defined by significant tumor progression (e.g. massive liver involvement, extrahepatic spread, or vascular invasion), clinical or functional deterioration, or development of a contraindication 17.
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