Lung Mean Dose Prediction in Transarterial Radioembolization (TARE): Superiority of [166Ho]-Scout Over [99mTc]MAA in a Prospective Cohort Study.

PURPOSE: Radiation pneumonitis is a serious complication of radioembolization. In holmium-166 ([166Ho]) radioembolization, the lung mean dose (LMD) can be estimated (eLMD) using a scout dose with either technetium-99 m-macroaggregated albumin ([99mTc]MAA) or [166Ho]-microspheres. The accuracy of eLMD based on [99mTc]MAA (eLMDMAA) was compared to eLMD based on [166Ho]-scout dose (eLMDHo-scout) in two prospective clinical studies. MATERIALS AND METHODS: Patients were included if they received both scout doses ([99mTc]MAA and [166Ho]-scout), had a posttreatment [166Ho]-SPECT/CT (gold standard) and were scanned on the same hybrid SPECT/CT system. The correlation between eLMDMAA/eLMDHo-scout and LMDHo-treatment was assessed by Spearman's rank correlation coefficient (r). Wilcoxon signed rank test was used to analyze paired data. RESULTS: Thirty-seven patients with unresectable liver metastases were included. During follow-up, none developed symptoms of radiation pneumonitis. Median eLMDMAA (1.53 Gy, range 0.09-21.33 Gy) was significantly higher than median LMDHo-treatment (0.00 Gy, range 0.00-1.20 Gy; p < 0.01). Median eLMDHo-scout (median 0.00 Gy, range 0.00-1.21 Gy) was not significantly different compared to LMDHo-treatment (p > 0.05). In all cases, eLMDMAA was higher than LMDHo-treatment (p < 0.01). While a significant correlation was found between eLMDHo-scout and LMDHo-treatment (r = 0.43, p < 0.01), there was no correlation between eLMDMAA and LMDHo-treatment (r = 0.02, p = 0.90). CONCLUSION: [166Ho]-scout dose is superior in predicting LMD over [99mTc]MAA, in [166Ho]-radioembolization. Consequently, [166Ho]-scout may limit unnecessary patient exclusions and avoid unnecessary therapeutic activity reductions in patients eligible for radioembolization. TRAIL REGISTRATION: NCT01031784, registered December 2009. NCT01612325, registered June 2012.

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.