Renal excretion of iodine-131 labelled meta-iodobenzylguanidine and metabolites after therapeutic doses in patients suffering from different neural crest-derived tumours.
Iodine-131 labelled meta-iodobenzylguanidine ([131I]MIBG) is used for diagnostic scintigraphy and radionuclide therapy of neural crest-derived tumours. After administration of therapeutic doses of [131I]MIBG (3.1-7.5 GBq) to 17 patients (n=32 courses), aged 2-73 years, 56%+/-10%, 73%+/-11%, 80%+/-10% and 83%+/-10% of the dose was cumulatively excreted as total radioactivity in urine at t=24 h, 48 h, 72 h and 96 h, respectively. Except for two adult patients, who showed excretion of 14%-18% of [131I]meta-iodohippuric acid ([131I]MIHA), the cumulatively excreted radioactivity consisted of >85% [131I]MIBG, with 6% of the dose excreted as free [131I]iodide, 4% as [131I]MIHA and 2.5% as an unknown iodine-131 labelled metabolite. Cumulative renal excretion rates of total radioactivity and of [131I]MIBG appeared to be higher in neuroblastoma and phaeochromocytoma patients than in carcinoid patients. Based on the excretion of small amounts of [131I]meta-iodobenzoic acid in two patients, a possible metabolic pathway for [131I]MIBG is suggested. The degree of metabolism was not related to the extent of liver uptake of radioactivity.
Wafelman
A R
AR
Department of Pharmacy, Slotervaart Hospital, Amsterdam, The Netherlands.
Hoefnagel
C A
CA
Maessen
H J
HJ
Maes
R A
RA
Beijnen
J H
JH
D019797:3-Iodobenzylguanidine; D000293:Adolescent; D000328:Adult; D000368:Aged; D002276:Carcinoid Tumor / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media / Q000378:metabolism*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000652:urine*; D007462:Iodobenzenes / Q000008:administration & dosage / Q000652:urine*; D007465:Iodohippuric Acid / Q000378:metabolism; D007668:Kidney / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009447:Neuroblastoma / Q000378:metabolism*; D010235:Paraganglioma / Q000378:metabolism; D010673:Pheochromocytoma / Q000378:metabolism*
D003287:Contrast Media; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D007465:Iodohippuric Acid; D019797:3-Iodobenzylguanidine