Dosimetry and biodistribution of an iodine-123-labeled somatostatin analog in patients with neuroendocrine tumors.
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.
O'Connor
M K
MK
Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905.
Kvols
L K
LK
Brown
M L
ML
Hung
J C
JC
Hayostek
R J
RJ
Cho
D S
DS
Vetter
R J
RJ
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
D007457:Iodine Radioisotopes; D015282:Octreotide