Dosimetry of 177Lu-DOTATATE administered into neuroendocrine tumors – An initial experience from India

Objectives Aim of this work was the calculation of radiation absorbed dose to lesion, kidneys, liver and spleen of patients affected by neuroendocrine tumors(NETs) treated with ¹⁷⁷Lu-DOTATATE.

Methods We enrolled eight patients (M/F:4/4 ) with mean age 40.25±15.54 affected by different types of NETs diagnosed with ⁶⁸Ga-DOTANOC PET-CT and biochemical markers.For radiation protection of kidneys,amino acid mixture was infused to each patient 30 m prior to therapeutic dose.3700MBq to 7400MBq of ¹⁷⁷Lu-DOTATATE was infused to each patient over 30 m.Each patients underwent nine whole Body Scan with Dual Head GE Mill VG Gamma Camera,at 30m(pre- void),4h,8h,12h,24h,48h, 96h,144h and 168h(Post- void) .Blood samples were taken at different time points post injection .Urine were collected at different time intervals post injection at 0-4h,4-8h, 8-12h,12- 24h and 24-48h .The organs involved in dosimetric calculation were lesion,kidney,liver and spleen. Dosimetric calculations were done using the OLINDA/EXM 1.0 software.

Results ¹⁷⁷Lu-DOTATATE showed a rapid urinary excretion within the first 4h after therapy,with 52.88% of the ¹⁷⁷Lu-DOTATATE administered being excreted.A physiological uptake of ¹⁷⁷Lu-DOTATATE was seen in all patients in Kidneys, liver and spleen.Radiation absorbed doses were calculated: 1.71±0.645mGy/MBq for Kidneys, 0.27±0.08mGy/MBq for liver,3.36±1.21mGy/MBq for Spleen and 0.059±0.049mGy/MBq for lesion.

Conclusions ¹⁷⁷Lu-DOTATATE is an effective radiopharmaceutical used in the treatment of NETs especially in inoperable and metastases. The radiation absorbed dose is acceptable and low for Kidneys.