Feasibility of Combination Intra-arterial Yttrium-90 and Irinotecan Microspheres in the VX2 Rabbit Model

Yttrium-90 Radioembolization in the VX2 Rabbit Model: Radiation Safety and Factors Influencing Delivery Efficiency

The purpose of this study was to define the optimal infusion parameters and operator radiation exposure for yttrium-90 (⁹⁰Y) radioembolization in the VX2 rabbit model of liver cancer. Forty-one rabbits with VX2 were treated with glass microspheres with vial sizes of 1, 3, and 5 GBq. The mean administered activity was 51.5 MBq (95% CI, 39.1-63.9). Delivery efficiency improved with 1 GBq versus with 3 GBq (residual 11.0% vs 46.4%, respectively; P = .0013) and improved with 1 GBq versus with 5 GBq (residual 11.0% vs 33.8%, respectively; P = .0060). The mean operator extremity exposure was 41.7 μSv/infusion. The optimal minimum infusion volume and rate was 49 mL and 21 mL/min, respectively. Fecal elimination occurred with microsphere uptake in the gallbladder at 1 and 2 weeks. ⁹⁰Y radioembolization can be safely and efficiently performed in the VX2 rabbit model. Methodological considerations as a "how-to" for the setup of a preclinical ⁹⁰Y laboratory are included to support future translational research.

Use of X-Ray Fluorescence Microscopy for Studies on Research Models of Hepatocellular Carcinoma

Introduction: TheraSphere^® microspheres containing yttrium ⁹⁰Y are among many radioembolization agents used clinically to reduce liver tumor burden, and their effects on cancer volume reduction are well-established. At the same time, concerns about off target tissue injury often limit their use. Deeper investigation into tissue distribution and long-term impact of these microspheres could inform us about additional ways to use them in practice.

Methods: Healthy rat liver and rabbit liver tumor samples from animals treated with TheraSpheres were sectioned and their elemental maps were generated by X-ray fluorescence microscopy (XFM) at the Advanced Photon Source (APS) synchrotron at Argonne National Laboratory (ANL).

Results: Elemental imaging allowed us to identify the presence and distribution of TheraSpheres in animal tissues without the need for additional sample manipulation or staining. Ionizing radiation produced by ⁹⁰Y radioactive contaminants present in these microspheres makes processing TheraSphere treated samples complex. Accumulation of microspheres in macrophages was observed.

Conclusions: This is the first study that used XFM to evaluate the location of microspheres and radionuclides in animal liver and tumor samples introduced through radioembolization. XFM has shown promise in expanding our understanding of radioembolization and could be used for investigation of human patient samples in the future.