Bland Embolization

Transarterial bland embolization (TAE, also known as HAE) is a catheter-based tumor treatment of the liver. In this procedure, a variety of embolizing agents (e.g., polyvinyl alcohol, gelfoam, acrylic copolymer gelatin particles, embospheres) can be delivered through the tumor’s feeding artery in order to completely occlude the tumor’s blood supply. The anti-tumor effects are solely based on tumor ischemia and infarction of tumor tissue, as no chemotherapeutic agents are administered. The rationale for the use of bland embolization for hepatocellular carcinoma(HCC) and/or other hyper-vascular tumors is based on the fact that normal liver receives a dual blood supply from the hepatic artery (25%) and the portal vein (75%). As the tumor grows, it becomes increasingly dependent on the hepatic artery for blood supply. Once a tumor nodule reaches a diameter of 2 cm or more, most of the blood supply is derived from the hepatic artery. Therefore, bland embolization and transarterial chemoembolization (TACE) consist of the selective angiographic occlusion of the tumor arterial blood supply with a variety of embolizing agents, with or without the precedence of local chemotherapy infusion. The occlusion by embolic particles results in tumor hypoxia and necrosis, without affecting the normal hepatic parenchyma. Transarterial bland embolization (TAE, also known as HAE) is a catheter-based tumor treatment of the liver. In this procedure, a variety of embolizing agents (e.g., polyvinyl alcohol, gelfoam, acrylic copolymer gelatin particles, embospheres) can be delivered through the tumor’s feeding artery in order to completely occlude the tumor’s blood supply. The anti-tumor effects are solely based on tumor ischemia and infarction of tumor tissue, as no chemotherapeutic agents are administered. The rationale for the use of bland embolization for hepatocellular carcinoma(HCC) and/or other hyper-vascular tumors is based on the fact that normal liver receives a dual blood supply from the hepatic artery (25%) and the portal vein (75%). As the tumor grows, it becomes increasingly dependent on the hepatic artery for blood supply. Once a tumor nodule reaches a diameter of 2 cm or more, most of the blood supply is derived from the hepatic artery. Therefore, bland embolization and transarterial chemoembolization (TACE) consist of the selective angiographic occlusion of the tumor arterial blood supply with a variety of embolizing agents, with or without the precedence of local chemotherapy infusion. The occlusion by embolic particles results in tumor hypoxia and necrosis, without affecting the normal hepatic parenchyma. Although TACE is considered the gold standard and TAE has largely been abandoned as a primary hepatic intra-arterial therapy for primary liver cancer, there are a few studies that suggest sufficient anti-tumor effects of TAE. In a series of 322 patients undergoing bland embolization for HCC with a median follow-up of 20 months, 1-, 2-, and 3- year overall survival rates were 66%, 46% and 33% respectively. When patients with extra-hepatic disease or portal vein involvement were excluded, overall 1-, 2- and 3-year survival rates rose to 84%, 66% and 51%, and median survival 40 months, respectively. A meta-analysis was performed of randomized controlled trials comparing the survival rates after TACE or TAE, which failed to demonstrate any significant difference between bland or chemoembolization. A later prospective randomized trial compared the response between patients who underwent DEB-TACE and patients who underwent TAE; this study demonstrated a better local tumor response with DEB-TACE versus TAE. However, a single blinded control trial compared the outcomes of TAE and DEB-TACE in a total of 101 patients with unresectable Okuda stage I or II HCC. Tumor response rate was the primary endpoint using Response Evaluation Criteria In Solid Tumors (RECIST) criteria, , while time to progression (TTP), progression free survival (PFS) and overall survival (OS) were defined as the secondary endpoints. In this study, no significant difference between the groups was noted and both groups showed comparable tumor response, PFS and TTP. The most common indication of this therapy is for treatment of unresectable primary hepatocellular carcinoma, based on anatomic distribution of disease, vascular invasion, underlying hepatic function or a combination of these factors. The majority of patients with HCC have underlying liver disease with resultant cirrhosis. Patients with normal liver function and, presumably, normal hepatic parenchyma may undergo resection of 75% to 80% of their liver without developing postoperative hepatic failure. Patients with underlying liver disease require a greater volume of liver remnant to maintain hepatic function, thus, tumors that might normally be resectable in patients with normal liver parenchyma may not be resectable in the presence of cirrhosis. The Child-Pugh nominal liver staging system is the most accurate in predicting survival of patients with unresectable HCC treated with TACE and TAE. Patients with Child-Pugh class C cirrhosis may be more likely to die of their underlying liver disease than of their HCC and are unlikely to tolerate arterial embolization well and therefore, embolization therapy is only indicated in patients with Child A or B cirrhosis. When evaluating a patient for embolization, both the severity of the underlying liver disease and the extent of the tumor being treated should be considered. In 1999, Llovet et al, proposed the Barcelona Clinic Liver Cancer (BCLC) staging classification as a means of both classifying patients and linking their stage to a specific treatment. Although selective embolization of a solitary well circumscribed HCC in a patient with Child Class B cirrhosis might be well tolerated, embolization of a hemi-liver in a Child A patient with multifocal hepatoma involving more than 75% of the liver and with portal vein tumor thrombus may result in hepatic failure and severe death. Patient with hepatic metastatic disease from neuroendocrine tumors, gastrointestinal stromal tumors other sarcomas, ocular melanoma, and a variety of “hypervascular” metastases (eg from breast cancer or renal cell cancer) may also be candidates for bland embolization, assuming the liver is the only site of disease, or when the procedure is being performed for palliation of symptoms. Since the purpose of hepatic embolization in these cases is to either treat symptoms or extend survival, patient who are asymptomatic from their secondary hepatic disease and who have disease elsewhere should probably not be considered candidates. Intra-arterial therapy based on ischemia induced by terminal vessel blockade should not be expected to be efficacious in patients with hypovascular tumors and has no proven role in the treatment of typical metastatic adenocarcinoma from most gastrointestinal malignancies.