Combined diagnostic imaging with 131I-metaiodobenzylguanidine and 111In-pentetreotide in carcinoid tumours

Abstract

Carcinoid tumours derived from the neural crest are usually associated with the symptoms of flushing and diarrhoea in the presence of liver metastases. Scintigraphs with 131 I-metaiodobenzylguanidine ( 131 I-MIBG) which is accumulated in the argentaffin granules of the cell, as well as with 111 In-pentetreotide for the imaging of somatostatin receptors on the cell surface, are positive in a large proportion of carcinoid patients. To evaluate the complementary role of both radionuclide tests, we studied 20 consecutive carcinoid patients: 14 with the characteristic carcinoid syndrome and 6 with tumour symptoms, such as pain or obstruction. A positive test was found in 84% with either 131 I-MIBG or 111 In-pentetreotide; the combination yielded a sensitivity of 95%. A positive correlation was found with the presence of the carcinoid syndrome, but not with 5-HIAA excretion. A positive test may help in adjusting treatment: either to predict the response to octreotide or to select patients for 131 I-labelled MIBG treatment. Application of a therapeutic dose of 111 In-pentetreotide may be limited by the high normal uptake in the kidneys.