111Indium-octreotide brain scintigraphy: a prognostic factor in skull base meningiomas treated with gamma knife radiosurgery.
OBJECTIVE
The purpose of this study is to prospectively investigate the prognostic role of somatostatin receptor scintigraphy (SRS) using an 111Indium-labelled somatostatin analogue, Octreotide, in skull base meningiomas (SBMs) treated with gamma knife (GK) radiosurgery.


METHODS
From December 1997 to March 2000, SRS was performed both before and within 1 year of radiosurgery on 12 patients. Semi-quantitative data were calculated as SRS index; the index decrease was arbitrarily considered significant above 10%. A potential correlation between the decrease in post/pre-GK SRS index and radiosurgical outcome was evaluated.


RESULTS
The follow-up period was at least 30 months in the whole series (median, 43 months). In all 12 patients, the pre-GK SRS index was always >1, averaging 3.73+/-2.9. A decrease in the post-GK average SRS index (2.35+/-1.5) was observed. The difference between the pre- and post-GK average values was statistically significant (p<0.03). At the 1st high-resolution magnetic resonance imaging (MRI) follow-up within 1 year of GK, there was no tumor shrinkage in any of the 12 patients of our series. A post/pre-GK SRS index decrease >10% was observed in 9 patients and <10% in 3. Delayed MRI follow-up documented tumor reduction in all 9 cases having an 111In uptake decrease >10%, with stable imaging in the others (p=0.00024).


CONCLUSIONS
Our preliminary findings suggest a prognostic correlation between a decrease in concentration of somatostatin receptors on meningioma cells within 1 year of radiosurgery and delayed meningioma shrinkage.
Nicolato
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Department of Neurosurgery, University Hospital, Verona, Italy.
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes; D008297:Male; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D008579:Meningioma / Q000000981:diagnostic imaging* / Q000601:surgery; D008875:Middle Aged; D011379:Prognosis; D019275:Radiopharmaceuticals; D016634:Radiosurgery; D019292:Skull Base Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D013004:Somatostatin / Q000031:analogs & derivatives*; D015899:Tomography, Emission-Computed, Single-Photon
D007205:Indium Radioisotopes; D019275:Radiopharmaceuticals; D013004:Somatostatin; C081788:pentetreotide