111Indium-octreotide brain scintigraphy: a prognostic factor in skull base meningiomas treated with gamma knife radiosurgery.

Abstract

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. 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. 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 (p10% was observed in 9 patients and 10%, with stable imaging in the others (p=0.00024). 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.