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: 90 Y-glass, 90 Y-resin, and 166 Ho-labeled poly(l-lactic acid) microsphere prescribed activity was calculated as per manufacturer recommendations. Posttreatment quantitative 90 Y PET/CT and quantitative 166 Ho 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 [18 F]FDG PET-based change in total lesion glycolysis. Hepatotoxicity was assessed using the radioembolization-induced liver disease classification. Results: Six 90 Y-glass, 8 90 Y-resin, and 7 166 Ho microsphere patients were included for analysis. The mean administered activity was 2.6 GBq for 90 Y-glass, 1.5 GBq for 90 Y-resin, and 7.0 GBq for 166 Ho microspheres. Tumor-absorbed dose and treated-normal-liver-absorbed dose were significantly higher for 90 Y-glass than for 90 Y-resin and 166 Ho microspheres (mean tumor-absorbed dose, 197 Gy for 90 Y-glass vs. 73 Gy for 90 Y-resin and 50 Gy for 166 Ho; mean treated-normal-liver-absorbed dose, 79 Gy for 90 Y-glass vs. 37 Gy for 90 Y-resin and 31 Gy for 166 Ho). 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 [18 F]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.