In Vivo Measurement and Characterization of a Novel Formulation of [(177)Lu]-DOTA-Octreotate

OBJECTIVE(S): Lutetium-177 can be made with high specific activity and with no other isotopes of lutetium present, referred to as “No Carrier Added” (NCA) (177)Lu. We have radiolabelled DOTA-conjugated peptide DOTA-(Tyr(3))-octreotate with NCA (177)Lu (“NCA-LuTATE”) and used it in nearly 40 therapeutic administrations for subjects with neuroendocrine tumours or meningiomas. In this paper, we report on our initial studies on aspects of the biodistribution and dosimetry of NCA-LuTATE from gamma camera 2D whole body (WB) and quantitative 3D SPECT (qSPECT) (177)Lu imaging. METHODS: Thirteen patients received 39 NCA-LuTATE injections. Extensive WB planar and qSPECT imaging was acquired at approximately 0.5, 4, 24 and 96 h to permit estimates of clearance and radiation dose estimation using MIRD-based methodology (OLINDA-EXM). RESULTS: The average amount of NCA-Lutate administered per cycle was 7839±520 MBq. Bi-exponential modelling of whole body clearance showed half lives for the fast & slow components of t(½)=2.1±0.6 h and t(½)=58.1±6.6 h respectively. The average effective dose to kidneys was 3.1±1.0 Gy per cycle. In eight patients completing all treatment cycles the average total dose to kidneys was 11.7±3.6 Gy. CONCLUSIONS: We have shown that NCA-LuTATE has an acceptable radiation safety profile and is a suitable alternative to Carrier-Added (177)Lu formulations. The fast component of the radiopharmaceutical clearance was closely correlated with baseline renal glomerular filtration rate, and this had an impact on radiation dose to the kidneys. In addition, it has less radioactive waste issues and requires less peptide per treatment.