title: Therapy using labelled somatostatin analogues: comparison of the absorbed doses with 111In-DTPA-D-Phe1-octreotide and yttrium-labelled DOTA-D-Phe1-Tyr3-octreotide.
abstract: OBJECTIVE
  We estimated the absorbed doses for (111)In-DTPA-D-Phe(1)-octreotide and (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide in the same patients in order to compare the potential effectiveness (tumour dose) and safety (kidney and red marrow dose) of these drugs for peptide-targeted radiotherapy of somatostatin receptor positive tumours.
  
  
  METHODS
  Six patients with neuroendocrine tumours underwent quantitative (111)In-DTPA-D-Phe(1)-octreotide SPECT and (86)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide PET scan at intervals of 1 week. All studies were performed with a co-infusion of amino acids for renal protection. PET and SPECT were reconstructed using iterative algorithms, incorporating attenuation and scatter corrections. Tissue uptakes (IA%) were measured and used to calculate residence times. Absorbed doses to tissues were estimated and the maximal allowed activity, defined as either the activity delivering 23 Gy to the kidneys (MAA(K)) or 2 Gy to the red marrow (MAA(RM)), was calculated and the resulting tumour absorbed doses were computed.
  
  
  RESULTS
  For the MAA(K) the mean absorbed dose to the red marrow was lower for (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide than for (111)In-DTPA-D-Phe(1)-octreotide (1.8+/-0.9 Gy vs. 6.4+/-1.6 Gy; P<0.001). The median absorbed dose to tumours for the MAA(K) was two-fold higher for (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide as compared to (111)In-DTPA-D-Phe(1)-octreotide (30.1 vs. 12.6 Gy; P<0.05). The median absorbed dose to tumours estimated for the MAA(RM) was 10-fold higher for (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide than for (111)In-DTPA-D-Phe(1)-octreotide (35.1 Gy vs. 3.9 Gy; P<0.05).
  
  
  CONCLUSIONS
  This direct intra-patient comparison confirms that the use of (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide is more appropriate for therapy of somatostatin receptor bearing tumours. When using (111)In-DTPA-D-Phe(1)-octreotide, the red marrow represents the major critical organ; this can result in significant toxicity if high activities have to be administered to obtain efficient tumour irradiation.
authors: Centre of Nuclear Medicine, University of Louvain Medical School, Avenue Hippocrate 54, Brussels, Belgium.
authors: Raffaella
authors: R
authors: Barone
authors: Stéphan
authors: S
authors: Walrand
authors: Mark
authors: M
authors: Konijnenberg
authors: Roelf
authors: R
authors: Valkema
authors: Larry K
authors: LK
authors: Kvols
authors: Eric P
authors: EP
authors: Krenning
authors: Stanislas
authors: S
authors: Pauwels
authors: François
authors: F
authors: Jamar
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000378:metabolism / Q000532:radiotherapy* / Q000556:secondary*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use; D004369:Pentetic Acid / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012062:Relative Biological Effectiveness; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: C442550:(111)indium-DTPA-D-phe octreoide; D007205:Indium Radioisotopes; D019275:Radiopharmaceuticals; D013004:Somatostatin; D004369:Pentetic Acid; D015282:Octreotide; C106246:Edotreotide