Evaluation of Safety, Biodistribution, and Dosimetry of a Long-Acting Radiolabeled Somatostatin Analog 177Lu-DOTA-EB-TATE With and Without Amino Acid Infusion

Kidney is considered to be one of the dose-limiting organs in peptide receptor radionuclide therapy (PRRT). Amino acid cocktail infusion has been applied to reduce renal absorbed dose by inhibiting the proximal tubular reabsorption of the radiopeptide. An Evans blue-modified 177 Lu-labeled octreotate ( 177 Lu-DOTA-EB-TATE) has an extended circulation in the blood, which may make the amino acid infusion unnecessary. The aim of this study was to evaluate the safety, biodistribution, and dosimetry of 177 Lu-DOTA-EB-TATE with and without amino acid infusion.Ten patients with metastatic neuroendocrine tumors were randomly divided into 2 groups. The effect of amino acid infusion on renal uptake was assessed in a crossover randomized setting. Group A received 177 Lu-DOTA-EB-TATE at a dose of 3.7 GBq without amino acid infusion for the first cycle and with amino acid infusion for the second cycle; group B received 177 Lu-DOTA-EB-TATE at a dose of 3.7 GBq with amino acid infusion for the first cycle and without amino acid infusion for the second cycle. All patients underwent serial whole-body planar imaging at 1, 24, 96, and 168 hours and SPECT scan at 24 hours after radioligand administration. Abdominal CT was performed 2 days before PRRT for SPECT/CT fusion. The dosimetry was calculated using the HERMES software. Dosimetry evaluation was compared on a between-group and intrapatient basis.Administrations of 177 Lu-DOTA-EB-TATE with or without amino acids were well tolerated. No grade 4 hematotoxicity was observed in any of the patients. Grade 3 thrombocytopenia was reported in 1 patient. No nephrotoxicity of any grade was recorded. No significant difference was observed in creatinine (75.1 ± 21.7 vs 67.5 ± 18.1 μmol/L, P = 0.128), blood urea nitrogen (4.5 ± 0.8 vs 5.1 ± 1.4 mmol/L, P = 0.612), or GFR (109.3 ± 25.2 vs 100.9 ± 24.9 mL/min, P = 0.398) before and after PRRT. For each cycle, there was no significant difference in whole-body effective dose, kidney effective dose, as well as residence time of the kidneys between group A and B ( P > 0.05). By intrapatient comparison, without and with amino acid infusion also did not show significant difference in whole-body effective dose (0.14 ± 0.05 vs 0.12 ± 0.04 mSv/MBq, P = 0.612), kidney effective dose (1.09 ± 0.42 vs 0.73 ± 0.31 mSv/MBq, P = 0.093), and residence time of the kidneys (2.95 ± 1.58 vs 3.13 ± 1.11 hours, P = 0.674).177 Lu-DOTA-EB-TATE PRRT with and without amino acid infusion demonstrated a favorable safety profile in neuroendocrine tumor patients. Administration of 177 Lu-DOTA-EB-TATE without amino acid infusion has acceptable slightly increased kidney absorbed dose and residence time of the kidneys, and does not affect kidney function. Further investigation in a larger cohort and long-term follow-up are warranted.