Terbium-161 a Promising Radionuclide for the Irradiation of Tumor Cells and Micrometastases: Monte Carlo Dose Assessment using CELLDOSE

E. HIDIE; MICHELE ARCANGELO QUINTO; P. ZANOTTI-FREGONARA; C. MORGAT; CHRISTOPHE CHAMPION

Conferencia; European Association of Nuclear Medicine; 2015

AIM: Radiopharmaceutical therapy, traditionally limited to the treatment of advanced metastatic disease, is now being considered in earlier settings to destroy minimal residual disease or occult micrometastases. The current study compares the effectiveness of 161Tb, 177Lu and 111In to irradiate micrometastases. 161Tb and 177Lu associate a medium-energy beta-emission with various conversion and Auger electrons. They also have a small photon component which allows imaging. By contrast, 111In is a γ-isotope for imaging that emits conversion and Auger electrons potentially helpful for therapy. METHODS: Electron dose was assessed in spheres of various sizes (from a 10-mm metastasis to a 10-μm single cell) with the Monte Carlo code CELLDOSE. The spheres were uniformly labeled with 161Tb, 177Lu or 111In. Doses were compared for a fixed amount of energy released per unit volume (1 MeV per μm3). The dose contribution from photons was neglected. RESULTS: In a 10-mm metastasis, the three isotopes exhibited equivalent dose deposit after normalization (1 MeV released per μm3). This dose was 154 Gy for 161Tb, 152 Gy for 177Lu and 155 Gy for 111In. However, for smaller micrometastases (