Transcatheter arterial chemoembolisation

Transcatheter arterial chemoembolisation (TACE), also known as transarterial chemoembolisation, is a minimally-invasive method of administratingadministering chemotherapy directly to a liver tumour 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 embolisation (TAE), also known as bland embolisation (i.e. without a chemotherapy agent added), is an alternative treatment option, and there is evidence that its efficacy is comparable to TACE.

History

Over 95% of the blood supply to a liver tumour is from the hepatic artery, whereas 80% of the blood supply to the normal liver parenchyma is from the portal vein ¹⁵. Therefore, embolisation of the hepatic artery can be performed in order to induce tumour necrosis while preserving background liver function. The technique of using embolisation 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

• 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 tumour infiltration throughout the liver 

• large burden of extra-hepatic metastases

• encephalopathy (indicating acute liver decompensation)

• anaphylaxis to iodinated contrast

Relative contraindications:

• portal vein thrombosis

• hepatic or renal failure

• uncorrectable coagulopathy

• significant arteriovenous shunting of blood through the tumour

Procedure

Chemoembolic particles are used to occlude the hepatic arterial supply to the tumour with resultant cytotoxic necrosis. This is achieved by superselective catheterisation of the tumour-feeding arteries using a microcatheter.

There is wide variability in the type of chemotherapy agent and embolisation 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 embolisation, 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 embolisation: particularly in the setting of an anatomical variant of the hepatic artery or arteriovenous shunting

• post-embolisation syndrome: occurs in 90% of patients

• myelosuppression

• infection including sepsis and hepatic abscess

• biloma

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 tumour 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 tumour, and thus the greater the survival benefit. Conversely, enhancing areas within the tumour are considered to represent residual viable tumour ⁵.

Four types of CT imaging patterns have been described ⁷:

• type I

  • Ia: homogeneous accumulation of iodised oil within the entire tumour and in the surrounding area - this type of accumulation indicates a good response to treatment

  • Ib: homogeneous accumulation of iodised oil within the entire tumour 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 currently no standardised 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 tumour progression (e.g. massive liver involvement, extrahepatic spread, or vascular invasion), clinical or functional deterioration, or development of a contraindication ¹⁷.

See also

• post-TACE assessment of hepatocellular carcinoma