Dosimetric Analyses of Kidneys, Liver, Spleen, Pituitary Gland, and Neuroendocrine Tumors of Patients Treated With 177Lu-DOTATATE

Objectives: The aim of this work was to calculate the radiation absorbed dose to kidneys, liver, spleen, pituitary gland, and neuroendocrine tumors (NETs) of patients treated with Lu-177-DOTATATE. Methods: We enrolled 61 patients (male/female patients, 40/21) with mean age of 48.1 +/- 15.3 years affected by different types of NETs diagnosed with Ga-68-DOTANOC PET-CT and biochemical markers. For radiation protection of kidneys, amino acid mixture (lysine and arginine) was coinfused; 3.7 to 7.4 GBq (100-200 mCi) of Lu-177-DOTATATE was infused to each patient over 30 minutes. Each patient underwent a series of 9 whole-body scans at 30 minutes (prevoid) and 4, 8, 12, 24, 48, 96, 144, and 168 h. The organs included in dosimetric calculation were kidney, liver, spleen, pituitary gland, and NETs. All dosimetric calculations were done using the OLINDA/EXM 1.0 software. Results: Physiological uptake of Lu-177-DOTATATE was seen in all patients in kidneys, liver, spleen, and pituitary gland. Radiation absorbed doses were calculated: 0.57 T 0.09 mGy/MBq for kidneys, 0.27 T 0.05 mGy/MBq for liver, 1.17 +/- 0.14 mGy/MBq for spleen, 0.058 +/- 0.011 mGy/MBq for pituitary gland, and 3.41 T 0.68 mGy/MBq for NETs. Conclusions: The maximum cumulative activity of Lu-177-DOTATATE that can be safely administered to a patient within permissible renal threshold in our study was found to be 40 GBq (1100 mCi). However, there are considerable interpatient differences in absorbed doses of all organs requiring individualized dosimetry for optimizing tumor dose.