Octreotide scintigraphy and catecholamine response to an octreotide challenge in malignant phaeochromocytoma

Octreotide scintigraphy has been reported to visualize chromaffine tumours. This study in patients with malignant phaeochromocytoma was designed to assess octreotide in comparison with standard m-iodobenzylguanidine (MIBG) scintigraphy and to study functional activity of somatostatin receptors. Finally, two cases of octreotide treatment are reported.

Open, prospective clinical trial.

In 12 patients with histologically proven malignant phaeochromocytoma, 111In-octreotide scintigraphy, 123I-MIBG scintigraphy and computed tomography were performed. In ten patients plasma catecholamine response to a single dose of octreotide (200 micrograms i.v.) was monitored up to 5 hours after injection. Two patients were treated with octreotide over several months.

Plasma catecholamines were measured by high performance liquid chromatography (HPLC). Scintigraphy was performed using a large field gamma camera and SPECT technique where appropriate.

At least one metastatic lesion was visualized by octreotide scintigraphy in eight patients while the remaining four patients had negative findings. In total, 43 out of 54 known metastases (79.6%) were detected by MIBG, 24 (44.4%) by octreotide. Nevertheless, octreotide scintigraphy detected six metastases that were negative by MIBG. There was no correlation between the results of octreotide scintigraphy and catecholamine suppression after i.v. octreotide. In two patients on octreotide treatment, symptomatic improvement, but not mass reduction, could be documented.

Octreotide scintigraphy behaves in part complementary to MIBG, thus, increasing diagnostic sensitivity. Presence of somatostatin receptors, as demonstrated by octreotide scintigraphy, does not necessarily predict functional activity or therapeutic response.