Comparison of 3 Different Therapeutic Particles in Radioembolization of Locally Advanced Intrahepatic Cholangiocarcinoma

Our objective was to compare 3 different therapeutic particles used for radioembolization in locally advanced intrahepatic cholangiocarcinoma. Methods:⁹⁰Y-glass, ⁹⁰Y-resin, and ¹⁶⁶Ho-labeled poly(l-lactic acid) microsphere prescribed activity was calculated as per manufacturer recommendations. Posttreatment quantitative ⁹⁰Y PET/CT and quantitative ¹⁶⁶Ho SPECT/CT were used to determine tumor-absorbed dose, whole-normal-liver–absorbed dose, treated-normal-liver–absorbed dose, tumor-to-nontumor ratio, lung-absorbed dose, and lung shunt fraction. Response was assessed using RECIST 1.1 and the [¹⁸F]FDG PET–based change in total lesion glycolysis. Hepatotoxicity was assessed using the radioembolization-induced liver disease classification. Results: Six ⁹⁰Y-glass, 8 ⁹⁰Y-resin, and 7 ¹⁶⁶Ho microsphere patients were included for analysis. The mean administered activity was 2.6 GBq for ⁹⁰Y-glass, 1.5 GBq for ⁹⁰Y-resin, and 7.0 GBq for ¹⁶⁶Ho microspheres. Tumor-absorbed dose and treated-normal-liver–absorbed dose were significantly higher for ⁹⁰Y-glass than for ⁹⁰Y-resin and ¹⁶⁶Ho microspheres (mean tumor-absorbed dose, 197 Gy for ⁹⁰Y-glass vs. 73 Gy for ⁹⁰Y-resin and 50 Gy for ¹⁶⁶Ho; mean treated-normal-liver–absorbed dose, 79 Gy for ⁹⁰Y-glass vs. 37 Gy for ⁹⁰Y-resin and 31 Gy for ¹⁶⁶Ho). The whole-normal-liver–absorbed dose and tumor-to-nontumor ratio did not significantly differ between the particles. All patients had a lung-absorbed dose under 30 Gy and a lung shunt fraction under 20%. The 3 groups showed similar toxicity and response according to RECIST 1.1 and [¹⁸F]FDG PET–based total lesion glycolysis changes. Conclusion: The therapeutic particles used for radioembolization differed from each other and showed significant differences in absorbed dose, whereas toxicity and response were similar for all groups. This finding emphasizes the need for separate dose constraints and dose targets for each particle.