An intrapatient comparison of 99mTc-EDDA/HYNIC-TOC with 111In-DTPA-octreotide for diagnosis of somatostatin receptor-expressing tumors.
The aim of this study was to compare the imaging abilities of the recently developed somatostatin analog, (99m)Tc-hydrazinonicotinyl-Tyr(3)-octreotide ((99m)Tc-HYNIC-TOC [(99m)Tc-TOC]), with (111)In-diethylenediaminepentaacetic acid-D-Phe(1)-octreotide ((111)In-OCT [Octreoscan]) in patients undergoing routine somatostatin receptor (SSTR) scintigraphy.


METHODS
Forty-one patients (20 men, 21 women; age range, 29-75 y; mean age, 56.7 y) with either histologically proven or biologically and clinically suspected endocrine tumors were enrolled in the study. Four groups were distinguished: (a) patients being evaluated for the detection and localization of neuroendocrine tumors (n = 6), (b) tumor staging (n = 19), (c) patients being investigated to determine the SSTR status of tumor lesions (n = 11), and (d) patient follow-up studies (n = 5). Each patient received a mean activity of 150 MBq (111)In-OCT and 350-400 MBq (99m)Tc-TOC. Scintigraphy with (99m)Tc-TOC was performed 4 h after injection and scintigraphy with (111)In-OCT was performed 4 and 24 h after injection. SPECT studies of areas of interest were performed 4 h after injection for both tracers as well as at 24 h after injection for (111)In-OCT. The time interval between the studies using each tracer ranged from 2 to 22 d (mean interval, 9.3 d).


RESULTS
(111)In-OCT and (99m)Tc-TOC showed an equivalent scan result in 32 patients (78%), 9 cases showed discrepancies (22%), false-negative results with (111)In-OCT were seen in 6 cases (14.6%), whereas (99m)Tc-TOC was false-positive in 2 cases (4.9%). (111)In-OCT was true-negative in both cases. The false-positive findings of the (99m)Tc-TOC studies were caused by nonspecific uptake in the bowel. In 1 case, (99m)Tc-TOC correctly identified a metastasis in the lumbar spine but both scan results were false-positive because of an inflammatory process. In 21 patients with SSTR-expressing tumors, the semiquantitative region-of-interest analysis showed that (99m)Tc-TOC achieved higher tumor-to-normal tissue ratios than (111)In-OCT.


CONCLUSIONS
This study revealed a higher sensitivity of (99m)Tc-TOC as compared with (111)In-OCT as an imaging agent for the localization of SSTR-expressing tumors. To avoid false-positive findings with (99m)Tc-OCT due to nonspecific tracer accumulation, additional scanning at 1-2 h after injection should be done.
Department of Nuclear Medicine, University of Innsbruck, Innsbruck, Austria. Institute of Biostatistics, University of Innsbruck, Innsbruck, Austria. Nuclear Medicine Research Laboratory, St. Bartholomew's Hospital, London, United Kingdom.
Michael
M
Gabriel
Clemens
C
Decristoforo
Eveline
E
Donnemiller
Hanno
H
Ulmer
Christine
C
Watfah Rychlinski
Stephen J
SJ
Mather
Roy
R
Moncayo
D000328:Adult; D000368:Aged; D004492:Edetic Acid / Q000031:analogs & derivatives*; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000737:chemistry / Q000000981:diagnostic imaging*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D015609:Organotechnetium Compounds; D004369:Pentetic Acid; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin / Q000032:analysis*
D007205:Indium Radioisotopes; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C415944:technetium Tc 99m-tricine-hydrazinonicotinyl-Phe(1)-Tyr(3)-octreotide; C026058:EDDA; D004369:Pentetic Acid; D004492:Edetic Acid; D015282:Octreotide