UC Berkeley

⁶⁸Ga-DOTA-TATE and 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 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 hr and 4 hr, 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 hr 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.