IN-111 (DTPA-OCTREOTIDE) SCINTIGRAPHY IN PATIENTS WITH CEREBRAL GLIOMAS

Somatostatin receptors (SR) have been identified in vitro in normal br ain tissue, in neuro-endocrine tumours and in cerebral gliomas WHO gra de 1 or 2 by autoradiography or using somatostatin-gold conjugates. In vivo, SR detection has become possible by scintigraphy applying the s omatostatin analogue octreotide, radio-labelled with Indium-111. It wa s supposed that expression of SR in cerebral gliomas corresponds to lo w grade tumour malignancy and that, in vivo, somatostatin receptor sci ntigraphy (SRS), could refine and improve the WHO grading system for c erebral gliomas. Nineteen patients with cerebral gliomas (grade 2: n = 8, grade 3: n = 3, grade 4: n = 8) were examined with In-111 (DTPA-oc treotide) to evaluate, whether SRS could improve the pre-operative est imation of tumour biology and the postoperative management. The result s of SRS were related with the histological findings and with the in v itro demonstration of somatostatin-binding sites on cultured tumour ce lls incubated with a somatostatin-gold conjugate. In vivo, none. of th e patients with glioma grade 2 showed enhanced tracer uptake in the SR S, whereas in vitro SR were detected in cultured tumour tissue in 5 ou t of 5 cases. Every patient with glioma grade 3 or 4 demonstrated a hi gh focal uptake of In-111 (DTPA-octreotide), as shown by SRS. Three pa tients with glioma grade 4, additionally examined with Tc-99m-DTPA, sh owed an increased tracer uptake within the tumour area when compared w ith results of SRS. In vitro, SR were detected on tumour cell surface in 5 out of 6 tissue samples from, patients with gliomas grade 3 or 4. One patient harbouring a cerebral abscess presented with a high focal tracer uptake in the SRS but with absence of somatostatin-binding sit es in vitro. We concluded. that in glioma patients enhanced tracer upt ake in receptor scintigraphy with In-111 (DTPA-octreotide) does not de pend on the presence of SR in tumour tissue but on the dysfunction of the blood-brain barrier. Thus, SRS does not improve the preoperative g lioma grading or postoperative management in patients with cerebral tu mours of glial origin.