Current status of embolic agents for liver tumor embolization.

Gelatin sponge and polyvinyl alcohol particles have been the most popular particulate embolic agents for transarterial chemoembolization (TACE) of liver tumors. Over the last decade, calibrated microspheres have been introduced and increasingly used in liver tumor embolization in Western countries. In addition, drug-eluting beads (DEB) have been introduced for sustained local drug release. Such long-awaited spherical embolic agents will be introduced in Japan in the near future. The advantages of these microspheres are that particles are uniform in size and shape, and easy to inject through a microcatheter. They can travel distally to vessels corresponding to the particle size; in other words, the occlusion level can be predicted according to the particle size chosen. Thus, new bland microspheres and DEB may bring a significant advancement to embolization for primary liver tumors as well as hepatic metastases from various cancers. However, at this point, the published data suggests that both conventional TACE and DEB-TACE are equally effective for treatment of unresectable hepatocellular carcinoma, when patients are carefully selected. Therefore, indication, patient selection, and embolization techniques will be essential in order to individually adapt newer embolic agents based on oncological, anatomical and technical considerations.