Dosimetric analyses of intra-arterial versus standard intravenous administration of 177Lu-DOTATATE in patients of well differentiated neuroendocrine tumor with liver-dominant metastatic disease.

Objective: The aim of the present study was to perform calculation of the absorbed doses to organs at risk and to neuroendocrine tumors and to determine whether hepatic intra-arterial (IA) injection of Lu-DOTATATE Peptide Receptor Radionuclide Therapy (PRRT) would achieve higher intratumoral concentrations than standard intravenous administration of Lu-DOTATATE.

Methods: 29 patients with Grade I-II, inoperable, metastatic gastro-entero-pancreatic neuroendocrine tumor (GEPNET) were prospectively identified and enrolled for the study. 15 patients of GEPNETs with liver-dominant metastatic disease and less than 3 sites of extrahepatic metastatic disease were administered a single dose of Lu-DOTATATE therapy through the selective catheterization of the hepatic artery (IA group). The other 14 patients received a single dose of Lu- DOTATATE through standard intravenous route (IV group). For dosimetry, whole-body γ (anterior and posterior planar acquisitions) and SPECT/CT scans of the abdomen at 2, 24 and 96 h post Lu-DOTATATE administration were acquired. Dosimetric calculations were done using the HERMES software.

Results: The mean dose per unit activity (DpA) in the liver and tumor lesions in the IA group differed significantly ( < 0.05) but differed insignificantly in spleen and kidneys ( > 05) with the IV group. The mean tumor/non-tumor concentration at 96 h was 76.83 ± 7.9 (range 10.2-251.3) in the IA group whereas it was 25.6 ± 5.9 (Range: 12-55) in the IV group. There was an average threefold increase in tumoral concentration over the standard intravenous group.

Conclusion: IA administration of Lu-DOTATATE results in higher concentration and absorbed dose in hepatic metastases in patients of GEPNETs as compared to a single dose of PRRT administered through standard IV route, and thus seems to be a powerful tool to improve the efficacy of PRRT.

Advances In Knowledge: Measurement of the dose received by the tumor lesions and the critical organs is of paramount importance for the prognostication of a radionuclide therapy. Scant data exist on the dosimetric impact of IA administration of the therapy with Lu-DOTATATE on the tumors and other organs, and this study would add an impact towards the better treatment outcome in patients of neuroendocrine tumor with liver-dominant metastatic disease.