%0 Journal Article %A Elif Hindié %A Paolo Zanotti-Fregonara %A Michele A. Quinto %A Clément Morgat %A Christophe Champion %T Dose Deposits from 90Y, 177Lu, 111In, and 161Tb in Micrometastases of Various Sizes: Implications for Radiopharmaceutical Therapy %D 2016 %R 10.2967/jnumed.115.170423 %J Journal of Nuclear Medicine %P 759-764 %V 57 %N 5 %X Radiopharmaceutical therapy, traditionally limited to refractory metastatic cancer, is being increasingly used at earlier stages, such as for treating minimal residual disease. The aim of this study was to compare the effectiveness of 90Y, 177Lu, 111In, and 161Tb at irradiating micrometastases. 90Y and 177Lu are widely used β−-emitting radionuclides. 161Tb is a medium-energy β− radionuclide that is similar to 177Lu but emits a higher percentage of conversion and Auger electrons. 111In emits γ-photons and conversion and Auger electrons. Methods: We used the Monte Carlo code CELLDOSE to assess electron doses from a uniform distribution of 90Y, 177Lu, 111In, or 161Tb in spheres with diameters ranging from 10 mm to 10 μm. Because these isotopes differ in electron energy per decay, the doses were compared assuming that 1 MeV was released per μm3, which would result in 160 Gy if totally absorbed. Results: In a 10-mm sphere, the doses delivered by 90Y, 177Lu, 111In, and 161Tb were 96.5, 152, 153, and 152 Gy, respectively. The doses decreased along with the decrease in sphere size, and more abruptly so for 90Y. In a 100-μm metastasis, the dose delivered by 90Y was only 1.36 Gy, compared with 24.5 Gy for 177Lu, 38.9 Gy for 111In, and 44.5 Gy for 161Tb. In cell-sized spheres, the dose delivered by 111In and 161Tb was higher than that of 177Lu. For instance, in a 10-μm cell, 177Lu delivered 3.92 Gy, compared with 22.8 Gy for 111In and 14.1 Gy for 161Tb. Conclusion: 177Lu, 111In, and 161Tb might be more appropriate than 90Y for treating minimal residual disease. 161Tb is a promising radionuclide because it combines the advantages of a medium-energy β− emission with those of Auger electrons and emits fewer photons than 111In. %U https://jnm.snmjournals.org/content/jnumed/57/5/759.full.pdf