Somatostatin receptor scintigraphy in central nervous system tumors: role of blood-brain barrier permeability.
Somatostatin receptors are expressed in meningiomas and low-grade gliomas, raising the hope that scintigraphy with 111In-DTPA-D-Phe1-octreotide might be helpful in the in vivo localization, differential diagnosis and postoperative/postradiotherapy brain tumor follow-up.


METHODS
Indium-111-DTPA-D-Phe1-octreotide scintigraphy and brain scintigraphy using 99mTc-DTPA as a nonspecific tracer for blood-brain barrier integrity were simultaneously performed in 60 patients with CNS tumors using dual-isotope acquisition mode SPECT. For 23 patients, the scintigraphic findings were also compared with in vitro somatostatin receptor autoradiography of surgical biopsy specimens.


RESULTS
In meningiomas (located outside the blood-brain barrier), the somatostatin receptor scan showed all tumors and scintigraphic signal intensity correlating with in vitro SSR density positive in all meningiomas. Less contrast was seen on 99mTc-DTPA scans. In all tumors inside the blood-brain barrier, the 111In-DTPA-D-Phe1-octreotide scan visualized the tumors with a disrupted blood-brain barrier, as seen by 99mTc-DTPA scintigraphy. Discrepancies, however, were observed between somatostatin receptor scintigraphy and in vitro receptor autoradiography.


CONCLUSIONS
Combined somatostatin receptor and 99mTc-DTPA scintigraphy may be helpful for noninvasive differentiation between meningiomas and other CNS tumors. False-negative scans were observed as a result of shielding by the intact blood-brain barrier. Interpretation of negative and positive somatostatin receptor scans in CNS tumors must therefore be done with caution.
Haldemann
A R
AR
Department of Nuclear Medicine, Inselspital, Berne, Switzerland.
Rösler
H
H
Barth
A
A
Waser
B
B
Geiger
L
L
Godoy
N
N
Markwalder
R V
RV
Seiler
R W
RW
Sulzer
M
M
Reubi
J C
JC
D000293:Adolescent; D000328:Adult; D000368:Aged; D001345:Autoradiography; D001812:Blood-Brain Barrier; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D004369:Pentetic Acid / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D011877:Radionuclide Imaging; D017481:Receptors, Somatostatin / Q000032:analysis*; D016284:Technetium Tc 99m Pentetate
D007205:Indium Radioisotopes; D017481:Receptors, Somatostatin; C071632:SDZ 215-811; D004369:Pentetic Acid; D015282:Octreotide; D016284:Technetium Tc 99m Pentetate