Abstract
(68)Ga-DOTA-TATE and (177)Lu-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 (68)Ga-DOTA-TATE and (177)Lu-DOTA-TATE in three laboratory mice bearing two IMR32 tumor xenografts expressing different levels of somatostatin receptors (SSTRs) on their shoulders and imaging both (68)Ga and (177)Lu simultaneously, we investigated the relationship between the uptake of (68)Ga-DOTA-TATE and (177)Lu-DOTA-TATE in organs and tumors. In addition, using the percent of injected activity (%IA) values of (68)Ga-DOTA-TATE at 0 hr and 4 hr, we investigated the correlation between (68)Ga-DOTA-TATE %IA and the time-integrated activity coefficients (TIACs) of (177)Lu-DOTA-TATE to estimate the organ-based and tumor-based doses of (177)Lu-DOTA-TATE. The results showed that the extrapolated clearance time of (68)Ga-DOTA-TATE linearly correlated with the TIACs of (177)Lu-DOTA-TATE in the IMR32-SSTR2 tumor, kidneys, brain, heart, liver, stomach and remainder body. The extrapolated %IA value at 0 hr of (68)Ga-DOTA-TATE linearly correlated with the TIACs of (177)Lu-DOTA-TATE in the IMR32 tumor and lungs. In our murine study, both kidneys and lungs were organs that showed high absorbed doses of (177)Lu-DOTA-TATE.