Simultaneous Imaging of Ga-DOTA-TATE and Lu-DOTA-TATE in Murine Models of Neuroblastoma

68Ga-labeled dodecane tetraacetic acid tyrosine-3-octreotate (68Ga-DOTA-TATE) and 177Lu-labeled DOTA-TATE (177Lu-DOTA-TATE) are radiolabeled somatostatin analogs used to detect or treat neuroendocrine tumors. They are administered separately for either diagnostic or therapeutic purposes but little experimental data for their biokinetics are measured simultaneously in the same biological model. By co-administering 68Ga-DOTA-TATE and 177Lu-DOTA-TATE in three laboratory mice bearing two Institute for Medical Research-32 (IMR32) tumor xenografts expressing different levels of somatostatin receptors (SSTRs) on their shoulders and imaging both 68Ga and 177Lu simultaneously, we investigated the relationship between the uptake of 68Ga-DOTA-TATE and 177Lu-DOTA-TATE in organs and tumors. In addition, using the percent of injected activity (%IA) values of 68Ga-DOTA-TATE at 0 h and 4 h, we investigated the correlation between 68Ga-DOTA-TATE %IA and the time-integrated activity coefficients (TIACs) of 177Lu-DOTA-TATE to estimate the organ-based and tumor-based doses of 177Lu-DOTA-TATE. The results showed that the extrapolated clearance time of 68Ga-DOTA-TATE linearly correlated with the TIACs of 177Lu-DOTA-TATE in the IMR32-SSTR2 tumor, kidneys, brain, heart, liver, stomach, and remainder body. The extrapolated %IA value at 0 h of 68Ga-DOTA-TATE linearly correlated with the TIACs of 177Lu-DOTA-TATE in the IMR32 tumor and lungs. In our murine study, both kidneys and lungs were organs that showed high absorbed doses of 177Lu-DOTA-TATE.