Transcatheter arterial chemoembolization

Transcatheter arterial chemoembolization is a minimally invasive procedure performed in interventional radiology to restrict a tumor's blood supply. Small embolic particles coated with chemotherapeutic drugs are injected selectively through a catheter into an artery directly supplying the tumor. These particles both block the blood supply and induce cytotoxicity, attacking the tumor in several ways. Transcatheter arterial chemoembolization is a minimally invasive procedure performed in interventional radiology to restrict a tumor's blood supply. Small embolic particles coated with chemotherapeutic drugs are injected selectively through a catheter into an artery directly supplying the tumor. These particles both block the blood supply and induce cytotoxicity, attacking the tumor in several ways. The radiotherapeutic analogue (combining radiotherapy with embolization) is called radioembolization or selective internal radiation therapy (SIRT). TACE derives its beneficial effect by two primary mechanisms. Most tumors within the liver are supplied by the proper hepatic artery, so arterial embolization preferentially interrupts the tumor's blood supply and stalls growth until neovascularization. Secondly, focused administration of chemotherapy allows for delivery of a higher dose to the tissue while simultaneously reducing systemic exposure, which is typically the dose limiting factor. This effect is potentiated by the fact that the chemotherapeutic drug is not washed out from the tumor vascular bed by blood flow after embolization. Effectively, this results in a higher concentration of drug to be in contact with the tumor for a longer period of time. Park et al. conceptualized carcinogenesis of hepatocellular carcinoma (HCC) as a multistep process involving parenchymal arterialization, sinusoidal capillarization, and development of unpaired arteries (a vital component of tumor angiogenesis). All these events lead to a gradual shift in tumor blood supply from portal to arterial circulation. This concept has been validated using dynamic imaging modalities by various investigators. Sigurdson et al. demonstrated that when an agent was infused via the hepatic artery, intratumoral concentrations were ten times greater compared to when agents were administered through the portal vein. Hence, arterial treatment targets the tumor while normal liver is relatively spared. Embolization induces ischemic necrosis of tumor causing a failure of the transmembrane pump, resulting in a greater absorption of agents by the tumor cells. Tissue concentration of agents within the tumor is greater than 40 times that of the surrounding normal liver. Transcatheter arterial chemoembolization has most widely been applied to HCC for patients who are not eligible for surgery. TACE has been shown to increase survival in patients with intermediate HCC by BCLC criteria. It has also been used as an alternative to surgery for resectable early stage HCC and in patients with regional recurrence of the tumor after previous resection. TACE may also be used to downstage HCC in patients who exceed the Milan criteria for liver transplantation. Other treated malignancies include neuroendocrine tumors, ocular melanoma, cholangiocarcinoma, and sarcoma. Transcatheter arterial chemoembolization plays a palliative role in patients with metastatic colon carcinoma. There is a possible benefit for liver-dominant metastases from other primary malignancies. TACE is an interventional radiology procedure performed in the angiography suite. The procedure involves gaining percutaneous transarterial access by the Seldinger technique to the hepatic artery with an arterial sheath, usually by puncturing the common femoral artery in the right groin and passing a catheter guided by a wire through the abdominal aorta, through the celiac trunk and common hepatic artery, and finally into the branch of the proper hepatic artery supplying the tumor.The interventional radiologist then performs a selective angiogram of the celiac trunk and possibly the superior mesenteric artery to identify the branches of the hepatic artery supplying the tumor(s) and threads smaller, more selective catheters into these branches. This is done to maximize the amount of the chemotherapeutic dose that is directed to the tumor and minimize the amount of the chemotherapeutic agent that could damage the normal liver tissue.