SOMATOSTATIN RECEPTOR IMAGING IN INTRACRANIAL TUMORS

The somatostatin analogue [In-111-DTPA-D- Phe(1)]-octreotide (In-111-o ctreotide) allows scintigraphic visualization of somatostatin receptor -expressing tissue. While it is well known that a large variety of tis sues express somatostatin receptors and In-111-octreotide scintigraphy has a clearly defined role in various neuroendocrine diseases, the cl inical value of In-111-octreotide scintigraphy in brain tumours is sti ll under clinical investigation. In 124 patients with 141 brain lesion s (63 meningiomas, 24 pituitary adenomas, 10 gliomas WHO class I and I I, 12 gliomas WHO class III and IV, 11 neurinomas and 2 neurofibromas, 7 metastases and 12 other varieties: three non-Hodgkin B-cell lymphom as, two epidermoids, one abscess, one angioleiomyoma, one chordoma, on e haemangiopericytoma, one osteosarcoma, one plasmacytoma and one pseu docyst), In-111-octreotide scintigraphy was performed 4-6 and 24 h aft er i.v. injection of 110-220 MBq In-111-octreotide. Planar images of t he head in four views with a 128x128 matrix and single-photon emission tomographic images (64x64 matrix) were acquired? and lesions were gra ded according to qualitative tracer uptake. Fifty-nine of the 63 menin giomas showed moderate to intense tracer uptake. Nine of 24 pituitary adenomas were visible; the remaining 15 did not show any tracer uptake . None of the class I and IT gliomas with an intact blood-brain barrie r were detected whereas 11/12 class III and IV gliomas showed In-111 o ctreotide uptake. None of the neurinomas or neurofibromas were positiv e. Five of seven metastases were classified as positive, as were the o steosarcoma: two of three non-Hodgkin B-cell lymphomas, one abscess, o ne angioleiomyoma, one chordoma and one haemangiopericytoma. The other varieties tone non-Hodgkin B-cell lymphoma, two epidermoids, one plas macytoma and one pseudocyst) did not show In-111-octreotide uptake. Th e results demonstrate that a large variety of intracranial lesions exp ress somatostatin receptors and therefore can be visualized by [In-111 -DTPA-D-Phe(1)]-octreotide scintigraphy. This technique can be valuabl e in the differentiation between meningiomas and pituitary adenomas, b ased on qualitative tracer uptake. [In-111-DTPA-D-Phe(1)]octreotide sc intigraphy allows differentiation between meningiomas and neurinomas o r neurofibromas and therefore provides complementary information to co mputed tomography or magnetic resonance imaging. Furthermore, this tec hnique allows differentiation between scar tissue and recurrent mening iomas postoperatively and can help in non-invasive tumour differentiat ion of multiple :intracranial lesions, which can be of value in defini ng the most adequate therapeutic strategy.