The use of the long-acting somatostatin analogue, octreotide acetate, in patients with islet cell tumors.

Octreotide lowers plasma concentrations of the marker peptide in the majority of patients with islet cell tumors. However, as described above the effect of octreotide on plasma concentrations of marker peptides is not necessarily related to the effect on symptoms. Nevertheless octreotide is capable of producing symptomatic relief in a large proportion of patients with islet cell tumor syndromes. The data on the effect of octreotide on the symptoms due to VIPoma and due to the carcinoid syndrome (presumably including some who have islet cell tumors) are strong and the drug has been approved for these indications by the Food and Drug Administration. With respect to the other islet cell tumor syndromes, the published data suggest that the utility of octreotide differs in the different syndromes. Insulinomas are usually single, benign, and can and should be removed surgically, resulting in cure. Octreotide therefore has no role to play in such patients, particularly since the response of insulinomas is variable. However in the 10 per cent of insulinomas that are malignant octreotide is certainly effective in at least a portion of cases, although as yet the true response rate and efficacy compared with diazoxide is not clear. Although octreotide is effective at reducing acid output, and thus improving symptoms in patients with Zollinger-Ellison syndrome, because of the effectiveness of histamine H2-receptor antagonists and omeprazole, there is no need for octreotide in this syndrome. For patients with glucagonoma, GHRHoma, Cushing's syndrome, and other rare islet cell tumor syndromes octreotide may well be of benefit and should be considered. The current data do not support the use of octreotide for an antitumor effect.