title: Bone marrow dosimetry in peptide receptor radionuclide therapy with [177Lu-DOTA(0),Tyr(3)]octreotate.
abstract: OBJECTIVE
  Adequate dosimetry is mandatory for effective and safe peptide receptor radionuclide therapy (PRRT). Besides the kidneys, the bone marrow is a potentially dose-limiting organ. The radiation dose to the bone marrow is usually calculated according to the MIRD scheme, where the accumulated activity in the bone marrow is calculated from the accumulated radioactivity of the radiopharmaceutical in the blood. This may underestimate the absorbed dose since stem cells express somatostatin receptors. We verified the blood-based method by comparing the activity in the blood with the radioactivity in bone marrow aspirates. Also, we evaluated the absorbed cross-dose from the source organs (liver, spleen, kidneys and blood), tumours and the so-called "remainder of the body" to the bone marrow.
  
  
  METHODS
  Bone marrow aspirates were drawn in 15 patients after treatment with [(177)Lu-DOTA(0),Tyr(3)]octreotate. Radioactivity in the bone marrow was compared with radioactivity in the blood drawn simultaneously. The nucleated cell fraction was isolated from the bone marrow aspirate and radioactivity was measured. The absorbed dose to the bone marrow was calculated. The results were correlated to the change in platelet counts 6 weeks after treatment.
  
  
  RESULTS
  A strong linear correlation and high agreement between the measured radioactivities in the bone marrow aspirates and in the blood was found (r=0.914, p<0.001). No correlation between the calculated absorbed dose in the bone marrow and the change in platelets was found. There was a considerable contribution from other organs and the remainder of the body to the bone marrow absorbed dose.
  
  
  CONCLUSIONS
  (1) After PRRT with [(177)Lu-DOTA(0),Tyr(3)]octreotate, the radioactivity concentration in the bone marrow is identical to that in the blood; (2) There is no significant binding of the radiopharmaceutical to bone marrow precursor stem cells; (3) The contribution of the cross dose from source organs and tumours to the bone marrow dose is significant; and (4) There is considerable variation in bone marrow absorbed dose between patients. These findings imply that for individual dose optimization, individual calculation of the bone marrow absorbed dose is necessary.
authors.affiliation: Department of Nuclear Medicine, Erasmus MC Rotterdam, Dr. Molewaterplein 40, NL-3015 GD, Rotterdam, The Netherlands. fforrer@uhbs.ch
authors.forename: Flavio
authors.initials: F
authors.lastname: Forrer
authors.forename: Eric P
authors.initials: EP
authors.lastname: Krenning
authors.forename: Peter P
authors.initials: PP
authors.lastname: Kooij
authors.forename: Bert F
authors.initials: BF
authors.lastname: Bernard
authors.forename: Mark
authors.initials: M
authors.lastname: Konijnenberg
authors.forename: Willem H
authors.initials: WH
authors.lastname: Bakker
authors.forename: Jaap J M
authors.initials: JJ
authors.lastname: Teunissen
authors.forename: Marion
authors.initials: M
authors.lastname: de Jong
authors.forename: Kirsten
authors.initials: K
authors.lastname: van Lom
authors.forename: Wouter W
authors.initials: WW
authors.lastname: de Herder
authors.forename: Dik J
authors.initials: DJ
authors.lastname: Kwekkeboom
mesh_terms: D001853:Bone Marrow / Q000000981:diagnostic imaging / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D018358:Neuroendocrine Tumors / Q000097:blood / Q000000981:diagnostic imaging / Q000276:immunology / Q000532:radiotherapy*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D009942:Organometallic Compounds / Q000627:therapeutic use*; D010976:Platelet Count; D011851:Radioactivity; D011874:Radiometry; D011879:Radiotherapy Dosage; D018000:Receptors, Peptide / Q000627:therapeutic use*; D017481:Receptors, Somatostatin / Q000378:metabolism; D013004:Somatostatin / Q000031:analogs & derivatives / Q000627:therapeutic use; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D009942:Organometallic Compounds; D018000:Receptors, Peptide; D017481:Receptors, Somatostatin; D013004:Somatostatin; C447941:lutetium Lu 177 dotatate; D015282:Octreotide