title: Quantitative 89Zr immuno-PET for in vivo scouting of 90Y-labeled monoclonal antibodies in xenograft-bearing nude mice.
abstract: Immuno-PET as a scouting procedure before radioimmunotherapy (RIT) aims at the confirmation of tumor targeting and the accurate estimation of radiation dose delivery to both tumor and normal tissues. Immuno-PET with (89)Zr-labeled monoclonal antibodies (mAbs) and (90)Y-mAb RIT might form such a valuable combination. In this study, the biodistribution of (89)Zr-labeled and (88)Y-labeled mAb ((88)Y as substitute for (90)Y) was compared and the quantitative imaging performance of (89)Zr immuno-PET was evaluated.
  
  
  METHODS
  Chimeric mAb (cmAb) U36, directed against an antigen preferentially expressed in head and neck cancer, was labeled with (89)Zr using the bifunctional chelate N-succinyldesferrioxamine B (N-sucDf) and with (88)Y using the bifunctional chelate p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (p-SCN-Bz-DOTA). The radioimmunoconjugates were coinjected in xenograft-bearing nude mice, and biodistribution was determined at 3, 24, 48, 72, and 144 h after injection. (89)Zr was evaluated and compared with (18)F in phantom studies to determine linearity, resolution, and recovery coefficients, using a high-resolution research tomograph PET scanner. The potential of PET to quantify cmAb U36-N-sucDf-(89)Zr was evaluated by relating image-derived tumor uptake data (noninvasive method) to (89)Zr uptake data derived from excised tumors (invasive method).
  
  
  RESULTS
  (89)Zr-N-sucDf-labeled and (88)Y-p-SCN-Bz-DOTA-labeled cmAb U36 showed a highly similar biodistribution, except for sternum and thigh bone at later time points (72 and 144 h after injection). Small differences were found in kidney and liver. Imaging performance of (89)Zr approximates that of (18)F, whereas millimeter-sized (19-154 mg) tumors were visualized in xenograft-bearing mice after injection of cmAb U36-N-sucDf-(89)Zr. After correction for partial-volume effects, an excellent correlation was found between image-derived (89)Zr tumor radioactivity and gamma-counter (89)Zr values of excised tumors (R(2) = 0.79).
  
  
  CONCLUSIONS
  The similar biodistribution and the favorable imaging characteristics make (89)Zr a promising candidate for use as a positron-emitting surrogate for (90)Y.
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Iris
authors.initials: I
authors.lastname: Verel
authors.forename: Gerard W M
authors.initials: GW
authors.lastname: Visser
authors.forename: Ronald
authors.initials: R
authors.lastname: Boellaard
authors.forename: Otto C
authors.initials: OC
authors.lastname: Boerman
authors.forename: Julliette
authors.initials: J
authors.lastname: van Eerd
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Snow
authors.forename: Adriaan A
authors.initials: AA
authors.lastname: Lammertsma
authors.forename: Guus A M S
authors.initials: GA
authors.lastname: van Dongen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000532:radiotherapy; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D008657:Metabolic Clearance Rate; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009928:Organ Specificity; D019047:Phantoms, Imaging; D016499:Radioimmunotherapy / Q000379:methods*; D011868:Radioisotopes / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013223:Statistics as Topic; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed / Q000295:instrumentation / Q000379:methods; D014183:Transplantation, Heterologous; D015021:Yttrium Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use; D015040:Zirconium / Q000493:pharmacokinetics*
chemical_list: D000911:Antibodies, Monoclonal; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes; D015040:Zirconium