123I-2-iodo-tyrosine, a new tumour imaging agent: human biodistribution, dosimetry and initial clinical evaluation in glioma patients.
OBJECTIVE
123I-2-iodo-tyrosine (123I-2IT) has been identified as a promising new amino acid tracer in animals. Uptake is mediated by LAT1 transport, which is increased in tumour cells. In this study we present the human biodistribution and first clinical results in glioma patients.


METHODS
For the biodistribution study, six male volunteers received 60-95 MBq 123I-2IT. Whole-body scans and blood and urine samples were obtained up to 24 h after injection; dosimetry was calculated using OLINDA 1.0 software. Initial clinical evaluation of 123I-2IT SPECT was performed in 35 patients with suspected or known glioma, either as primary diagnosis or for detection of recurrence. Tumour-to-background (T/B) ratios were calculated for semi-quantitative analysis. The results were correlated with clinical and MRI follow-up data or histology.


RESULTS
123I-2IT showed both renal and intestinal clearance. Bladder (0.12 mGy/MBq) and small intestine (0.03 mGy/MBq) received the highest absorbed doses. The effective dose equivalent and effective dose were estimated at 0.020 and 0.016 mSv/MBq, respectively. In patients, 123I-2IT SPECT did not differentiate between neoplastic and non-neoplastic lesions after an indeterminate MRI. In follow-up of known glioma, 13/15 patients with disease recurrence had increased T/B values (range 1.39-3.91). Out of seven recurrence-negative patients, two showed an important increase in T/B, in one case due to radionecrosis (T/B 1.59) and in the other probably due to residual but stable disease (T/B 2.07).


CONCLUSIONS
123I-2IT has a favourable biodistribution for a tumour imaging agent. It shows increased uptake in central nervous system glioma and is potentially useful in the follow-up of glioma patients.
Keyaerts
Marleen
M
Department of Nuclear Medicine, Academic Hospital, Vrije Universiteit Brussel AZ-VUB, Laarbeeklaan 101, 1090 Brussels, Belgium. Marleen.Keyaerts@vub.ac.be
Lahoutte
Tony
T
Neyns
Bart
B
Caveliers
Vicky
V
Vanhove
Chris
C
Everaert
Hendrik
H
Kersemans
Ken
K
Franken
Philippe R
PR
Mertens
John
J
Bossuyt
Axel
A
D000293:Adolescent; D001822:Body Burden; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D005910:Glioma / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D007470:Monoiodotyrosine / Q000493:pharmacokinetics*; D009928:Organ Specificity; D010865:Pilot Projects; D011829:Radiation Dosage; D011874:Radiometry; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution
C492712:2-iodotyrosine; D019275:Radiopharmaceuticals; D007470:Monoiodotyrosine