title: Dosimetry and biodistribution of an iodine-123-labeled somatostatin analog in patients with neuroendocrine tumors.
abstract: A modified method for the preparation of a radiolabeled analog of somatostatin (123I-octreotide) is described. The pharmacokinetics and dosimetry of this analog were evaluated in patients with neuroendocrine tumors. Thirty patients had multiple blood and urine samples and sequential anterior and posterior whole-body scintigraphy up to 40 hr postinjection of 123I-octreotide. Region of interest analysis of the whole-body images was used to determine organ and tumor doses. The 123I-octreotide was rapidly cleared from the blood with a T 1/2 of 10 min by the hepatobiliary system. By 40 hr, approximately 55% was eliminated in the feces. The gallbladder wall received the highest dose (0.48 rad/mCi), with other organs receiving doses of 0.12 rad/mCi or less. Tumors were identified in 25 of 28 satisfactory studies. Tumor doses ranged from 0.1 to 0.6 rad/mCi. Calculations with 131I instead of 123I indicated that the gallbladder wall would receive 2 rad/mCi, while average tumor doses would range from 0.9 to 5.0 rad/mCi. Iodine-123-octreotide is a useful agent for the visualization of neuroendocrine tumors. The rapid washout of this agent from tumors precludes the possibility of radiotherapy with 131I-octreotide in these patients.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: M K
authors.initials: MK
authors.lastname: O'Connor
authors.forename: L K
authors.initials: LK
authors.lastname: Kvols
authors.forename: M L
authors.initials: ML
authors.lastname: Brown
authors.forename: J C
authors.initials: JC
authors.lastname: Hung
authors.forename: R J
authors.initials: RJ
authors.lastname: Hayostek
authors.forename: D S
authors.initials: DS
authors.lastname: Cho
authors.forename: R J
authors.initials: RJ
authors.lastname: Vetter
mesh_terms: D004701:Endocrine Gland Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D009423:Nervous System Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism*; D015282:Octreotide / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D011877:Radionuclide Imaging
chemical_list: D007457:Iodine Radioisotopes; D015282:Octreotide