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

Purpose: Radiation pneumonitis is a serious complication of radioembolization. In holmium-166 ([Ho]) radioembolization, the lung mean dose (LMD) can be estimated (eLMD) using a scout dose with either technetium-99 m-macroaggregated albumin ([Tc]MAA) or [Ho]-microspheres. The accuracy of eLMD based on [Tc]MAA (eLMD) was compared to eLMD based on [Ho]-scout dose (eLMD) in two prospective clinical studies.

Materials And Methods: Patients were included if they received both scout doses ([Tc]MAA and [Ho]-scout), had a posttreatment [Ho]-SPECT/CT (gold standard) and were scanned on the same hybrid SPECT/CT system. The correlation between eLMD/eLMD and LMD 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 eLMD (1.53 Gy, range 0.09-21.33 Gy) was significantly higher than median LMD (0.00 Gy, range 0.00-1.20 Gy; p < 0.01). Median eLMD (median 0.00 Gy, range 0.00-1.21 Gy) was not significantly different compared to LMD (p > 0.05). In all cases, eLMD was higher than LMD (p < 0.01). While a significant correlation was found between eLMD and LMD (r = 0.43, p < 0.01), there was no correlation between eLMD and LMD (r = 0.02, p = 0.90).

Conclusion: [Ho]-scout dose is superior in predicting LMD over [Tc]MAA, in [Ho]-radioembolization. Consequently, [Ho]-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.