In the context of radiology, transarterial chemoembolization (TACE) represents a minimally invasive procedure used to treat liver cancer that can no longer be operated on. In most cases, it can no longer cure liver cancer. However, it does help prolong the patient’s life.
What is transarterial chemoembolization?
With the help of transarterial chemoembolization (TACE), inoperable hepatic carcinoma (HCC) can be treated minimally invasively. The procedure is also suitable for the treatment of liver metastases from other carcinomas, such as neuroendocrine tumors in particular. The term “transarterial chemoembolization” already indicates how this procedure works. The arteries supplying the cancer are temporarily blocked (embolization) by means of small particles in order to slow down the blood supply. At the same time, the carcinoma is targeted with chemotherapeutic agents. Both the lack of oxygen from embolization and the targeted injection with chemotherapeutic agents are intended to cause the cancer to die. As a rule, however, liver carcinoma can no longer be cured because it usually develops in a liver that is already severely affected by cirrhosis. A cure is only successful in the rare cases where there are only single small nodules. In the vast majority of cases, however, this treatment has palliative significance. It serves to prolong life. Furthermore, transarterial chemoembolization can also be used as a bridge therapy until successful liver transplantation.
Function, effect, and goals
Transarterial chemoembolization is used only for primary liver carcinomas or for metastases in the liver. It exploits the fact that hepatocellular carcinomas are supplied almost exclusively by small arterial vessels. A healthy liver is nourished 75 percent by the portal vein and 25 percent by the hepatic artery. However, hepatic carcinomas and metastases in the liver are disconnected from the portal vein. They are supplied 95 percent by the hepatic artery. This is done via small arterial vessels that branch off from the hepatic artery. Within these arterial blood vessels, TACE is designed to temporarily stop blood flow by blocking it while the chemotherapy drug takes effect. To achieve this, a so-called exploratory catheter is placed in the inguinal artery (femoral artery) at the outlet to the liver supply. With the help of contrast media, the tumor and the position of the catheter tip can be visualized. Now, a catheter is pushed into the hepatic artery via the probing catheter and placed at the correct position to the tumor. The closer the catheter is to the carcinoma, the better it can be targeted. Closer positioning allows for more aggressive local chemotherapy. There are also catheters that can be pushed even deeper into small arteries that supply the tumor. If the catheter is placed too far from the tumor, there is a risk that the blood supply to the pancreas or small intestine may also be cut off. Today, there are still no universally accepted standards regarding the choice of embolisates and chemotherapeutic agents. Lipiodol or spherical gelatin or plastic particles are frequently used as embolisates. Lipiodol is an iodine-containing oily liquid that temporarily blocks blood vessels by droplet formation. Both the oil droplets and the plastic or gelatin particles can slow blood flow. As a result, the tumor is undersupplied with oxygen. At the same time, the chemotherapeutic agent is also injected through the catheter. The main chemotherapeutic agents used are mitomycin C, carboplatin or doxorubicin. This treatment is followed by further embolization. Transarterial chemoembolization usually consists of the combination of embolization with chemotherapy. In individual cases, embolization is also performed without chemotherapy or local chemotherapy is performed without embolization. However, the best long-term results have been achieved by combining the two procedures. It is recommended that TACE treatment be repeated several times, depending on the success of the therapy, in order to target as many cancer cells as possible. Studies have shown that the two-year survival rate increases significantly compared to non-treated patients.Thus, significantly more affected patients have the chance to have a liver transplant for complete healing by extending the bridging time. TACE can also be combined with other therapy methods as an alternative. These include percutaneous ethanol injection therapy (PEI), radiofrequency ablation (RFA), selective internal radiotherapy (SIRT), or sorafenib chemotherapy. Percutaneous ethanol injection therapy involves injecting a 95 percent ethanol solution through the skin into the tumor. Radiofrequency ablation works by using an applicator inserted into the tissue, which destroys the diseased tissue by generating heat. The chemotherapeutic agent sorafenib is applied orally via tablets. These procedures can be used in conjunction with embolization. The SIRT procedure uses beads laced with radioactive yttrium, which both destroy the tumor by irradiation and have a simultaneous embolizing effect.
Risks, side effects, and hazards
However, there are contraindications to transarterial chemoembolization. For example, this procedure should not be used in the presence of a pedunculated tumor type, blood clotting disorders, allergies to the contrast agent, heart failure, or severe cardiac arrhythmias. TACE is also contraindicated in cases of severe tumor involvement of the liver or tumor infiltration into the hepatic veins, portal vein, and adjacent organs. Of course, this also applies in cases of severe liver insufficiency or poor general health. It must also be emphasized that the success of the procedure depends on the stage of the disease. The more tumor foci are present, the more costly the treatment becomes. Some cases represent borderline cases, in which it is often difficult to decide whether treatment is still effective at all or even already counterproductive.
