title: Twins in spirit part IV - [177Lu] high affinity DOTATATE. A promising new tracer for peptide receptor radiotherapy?
abstract: OBJECTIVE
  Besides the use of somatostatin analogues, small molecules like sunitinib and everolimus as well as conventional chemotherapy, peptide receptor radiotherapy (PRRT) using radiolabelled somatostatin analogues has gained an important role in the treatment of inoperable, metastasized neuroendocrine tumours (NET). There are various radiotracers in use. Based on our experience with the PET tracer [68Ga]DOTA-3-iodo-Tyr3-octreotate ([68Ga]HA-DOTATATE), a DOTATATE derivative with an increased binding affinity to hsst5, the current retrospective analysis is exploring the therapeutic potential of [177Lu]HA-DOTATATE.
  
  
  METHODS
  Eighteen patients with metastatic NET (G1/G2) were treated using [177Lu]DOTATATE and/or [177Lu]HA-DOTATATE, and dosimetric results of both tracers were compared.
  
  
  RESULTS
  Using [177Lu]HA-DOTATATE, a mean tumour dose of 5.34 Gy/GBq (median 2.53 Gy/GBq; range 0.89-33.3 Gy/GBq) was achieved, while [177Lu]DOTATATE delivered a tumour dose of 5.53 Gy/GBq (median 2.70 Gy/GBq; range 0.44-15.3 Gy/GBq). Organ doses for [177Lu]HA-DOTATATE vs. [177Lu]DOTATATE were as follows: kidney 2.31 ± 0.85 vs. 2.03 ± 0.96 Gy/GBq, liver 1.06 ± 0.79 vs. 1.67 ± 1.73 Gy/GBq, spleen 3.89 ± 4.04 vs. 4.50 ± 3.69 Gy/GBq and whole body 0.16 ± 0.10 Gy/GBq vs. 0.15 ± 0.08 Gy/GBq. Tumour-to-kidney dose ratio was slightly higher for [177Lu]DOTATATE (2.4 ± 5.6) compared to [177Lu]HA-DOTATATE (1.5 ± 3.6).
  
  
  CONCLUSIONS
  Both tracers showed marked inter-patient variation in their dosimetry, and no significant differences in dosimetry of [177Lu]HA-DOTATATE and [177Lu]DOTATATE were observed when taking all patients into account. Thus, [177Lu]HA-DOTATATE appears viable for PRRT, although it was marginally inferior regarding kidney dose and tumour-to-kidney dose ratio compared to the established [177Lu]DOTATATE.
authors.affiliation: Claudia Brogsitter, Fetscherstr. 74, 01307 Dresden, Germany, Tel. +49-351-458 4160, Fax. +49-351-458 5347, E-Mail: Claudia.Brogsitter@uniklinikum-dresden.de.
authors.forename: Claudia
authors.initials: C
authors.lastname: Brogsitter
authors.forename: Holger
authors.initials: H
authors.lastname: Hartmann
authors.forename: Gerd
authors.initials: G
authors.lastname: Wunderlich
authors.forename: Margret
authors.initials: M
authors.lastname: Schottelius
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Wester
authors.forename: Jörg
authors.initials: J
authors.lastname: Kotzerke
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000556:secondary*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D009942:Organometallic Compounds / Q000627:therapeutic use*; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; C447941:lutetium Lu 177 dotatate; D015282:Octreotide
keywords: DOTATATE; HA-DOTATATE; PRRT; dosimetry