OCTREOTIDE SCINTIGRAPHY AND CATECHOLAMINE RESPONSE TO AN OCTREOTIDE CHALLENGE IN MALIGNANT PHEOCHROMOCYTOMA

OBJECTIVE Octreotide scintigraphy has been reported to visualize chrom affine tumours. This study in patients with malignant phaeochromocytom a was designed to assess octreotide in comparison with standard m-iodo benzylguanidine (MIBG) scintigraphy and to study functional activity o f somatostatin receptors, Finally, two cases of octreotide treatment a re reported. DESIGN Open, prospective clinical trial. PATIENTS In 12 p atients with histologically proven malignant phaeochromocytoma, In-111 -octreotide scintigraphy, I-123-MIBG scintigraphy and computed tomogra phy were performed. In ten patients plasma catecholamine response to a single dose of octreotide (200 mu g i.v.) was monitored up to 5 hours after injection. Two patients were treated with octreotide over sever al months. MEASUREMENTS Plasma catecholamines were measured by high pe rformance liquid chromatography (HPLC), Scintigraphy was performed usi ng a large field gamma camera and SPECT technique where appropriate. R ESULTS At least one metastatic lesion was visualized by octreotide sci ntigraphy in eight patients while the remaining four patients had nega tive findings. In total, 43 out of 54 known metastases (79.6%) were de tected by MIBG, 24 (44.4%) by octreotide, Nevertheless, octreotide sci ntigraphy detected six metastases that were negative by MIBG, There wa s no correlation between the results of octreotide scintigraphy and ca techolamine suppression after i.v. octreotide, In two patients on octr eotide treatment, symptomatic improvement, but not mass reduction, cou ld be documented. CONCLUSIONS Octreotide scintigraphy behaves in part complementary to MIBG, thus increasing diagnostic sensitivity, Presenc e of somatostatin receptors, as demonstrated by octreotide scintigraph y, does not necessarily predict functional activity or therapeutic res ponse.