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The scientific rationale for embolization for the treatment of hepatocellular carcinoma (HCC), explains Jeff Geschwind, MD, is that liver tumors draw their blood supply from the hepatic artery. Embolization uses this blood supply route as a roadway to get to the tumor and deliver chemicals or radioactive components directly to the tumor itself. This strategy, therefore, preserves not only the systemic organs, but also much of the normal liver tissue.
Chemoembolization, also known as trans-arterial chemoembolization (TACE) can be performed using conventional and drug-eluting beads. The conventional type uses the lipiodol chemotherapy emulsification process followed by some degree of embolization. This method preserves the sanctity of the emulsion for an extended period of time, Geschwind notes, which allows the drugs to remain within the tumor longer and exert their effect. The drug-eluting bead approach uses polymer-based microspheres that can elute the drugs over a long period of time.
An additional approach is known as bland embolization, which distally cuts off the blood supply, without the use of chemotherapy. This approach blocks the blood vessels using an occlusive device, causing a massive ischemic even that results in tumor death.
Radioembolization uses an approach similar to chemoembolization; however, radiation is administered instead of a chemotherapy, states Geschwind. There are 2 types of radiation devices commonly used, both administering Yttrium 90 microspheres. The difference between the 2 devices is the activity level per bead. One device, from Canada, has very high activity per bead, requiring fewer microspheres to exert a radioactive effect. The other device, from Australia, is less activity per bead, requiring more beads. As a result of more beads, it is presumed this approach will have a greater embolic effect. In the context of HCC, radioembolization has not been shown to be convincingly superior to chemoembolization, but there is a niche application in some cases, notes Geschwind.
One of the challenges to using embolization is defining the best patient candidates. The criteria for patient selection in the trials studying these approaches was relatively strict in terms of tumor size, tumor burden, and vascular involvement, notes Richard Finn, MD. The trials helped to establish the utility of chemoembolization, states Geschwind, finding that the patients who benefited most were those who did not have portal invasion, and had a performance status of 0. This comprises 40% of the patients with HCC worldwide, Geschwind adds.