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

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 131I-metaiodobenzylguanidine (131I-MIBG) which is accumulated in the argentaffin granules of the cell, as well as with 111In-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 131I-MIBG or 111In-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 131I-labelled MIBG treatment. Application of a therapeutic dose of 111In-pentetreotide may be limited by the high normal uptake in the kidneys.