Surgically Unresectable and Chemotherapy-Refractory Metastatic Liver Carcinoma: Treatment with Yttrium-90 Microsphere Followed by Assessment with Positron Emission Tomography

Detection of metastatic cancer to the liver with positron emission tomography (PET) or computed tomography (CT) usually signifies an ominous sign for patients with colorectal cancer (Fernandez et al., 2004; Arulampalam et al., 2001) and other solid cancers (Silvestri et al., 2003; Eubank et al., 2002). Surgically unresectable and chemotherapy refractory metastatic cancer to the liver often represents an end-stage event. For these patients, a wide variety of local and regional therapies have been developed from the experience of treating hepatocellular carcinoma for the purpose of providing local control of liver tumors while sparing essential vascular structures, liver parenchyma, and adjacent organs (Rilling and Drooz, 2002). Yttrium-90 glass and resin micro-spheres have been shown to be chemically durable for in vivo delivery of β-radiation (Drbe and Day, 1993). Recently hepatic intraarterial infusion of Yttrium-90 glass or resin microspheres has been introduced for palliating unresectable hepatocellu-lar carcinoma (Dancey et al., 2000; Ho et al., 1997). Their use in palliation of unresectable liver metastases from solid cancers has been shown to be promising (Wong et al., 2004, 2005). Two commercial products of these microspheres are available in glass matrix (20–30 μm, 3.6 g/ dl, 2,500 Bq/particle, THERA-Sphere®, MDS Nordion, Ottawa, Canada) or resin bound (20–60 μm, 1.6 g/dl, 50 Bq/particle, SIR-Spheres®, Sirtex Medical, New South Wales, Australia) forms (Wong et al., 2006). Both the glass or resin microspheres are introduced via catheterization of the hepatic artery that supplies the majority of the blood. Tumors and the microspheres are trapped in the tumor capillary bed where they exert a local radio-therapeutic effect. Yttrium-90, a pure beta-emitter with a physical half-life of 64.2 h, decays to stable zirconium-90. The average energy of the beta emissions from the Yttrium-90 is 0.9367 MeV, with an average penetration range of 2.5 mm in tissue (Dancey et al., 2000).