title: Improved effect of 131I-MIBG treatment by predosing with non-radiolabeled MIBG in carcinoid patients, and studies in xenografted mice.
abstract: BACKGROUND
  131I-meta-iodobenzylguanidine (MIBG) has been used with success for the palliation of metastatic carcinoid. To qualify more patients for this treatment, we evaluated the effect of predosing with non-radiolabeled MIBG on 131I-MIBG tumour targeting in carcinoid patients and in mice with BON human carcinoid xenografts.
  
  
  METHODS
  Ten carcinoid patients with a faint tumour imaging on a diagnostic 131I-MIBG scan (1 mCi = 37 MBq, 5 mg MIBG) received non-radiolabeled MIBG prior to a second scintigraphy. In case of improved tumour targeting patients were treated with 200 mCi (7.4 GBq) 131I-MIBG following a pharmacological predose of 20-40 mg/m2 MIBG.
  
  
  RESULTS
  In six patients. highly increased 'tumour/non-tumour' ratios were seen due to reduced levels in normal tissues and increased tumour accumulation. The combined treatment applied in five patients, considerably improved symptoms in all (duration 6-12 months), accompanied by biochemical response in three. In BON carcinoid xenografted mice, MIBG was injected intraperitoneally followed by intravenous 125I-MIBG with similar findings: increased 'tumour/non-tumour' radioactivity ratios by 1.5-3-fold.
  
  
  CONCLUSIONS
  Predosing with non-radiolabeled MIBG resulted in improved 131I-MIBG tumour targeting, prolonged palliation and encouragingly often biochemical responses in carcinoid.
authors.affiliation: Department of Gastroenterology, Netherlands Cancer Institute/Antoni van Leeuwenhoek Ziekenhuis, Amsterdam. b_taal@nki.nl
authors.forename: B G
authors.initials: BG
authors.lastname: Taal
authors.forename: C
authors.initials: C
authors.lastname: Hoefnagel
authors.forename: H
authors.initials: H
authors.lastname: Boot
authors.forename: R
authors.initials: R
authors.lastname: Valdés Olmos
authors.forename: M
authors.initials: M
authors.lastname: Rutgers
mesh_terms: D019797:3-Iodobenzylguanidine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D002276:Carcinoid Tumor / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D004341:Drug Evaluation; D005260:Female; D006801:Humans; D007456:Iodine Isotopes / Q000008:administration & dosage* / Q000493:pharmacokinetics; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014018:Tissue Distribution; D016896:Treatment Outcome; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D007456:Iodine Isotopes; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine