Scintiscans and carcinoid tumors.

Abstract

The presence of somatostatin receptors on carcinoid tumors mediates imaging of tumor extent and inhibition of tumor growth and marker secretion. This prospective study aimed to evaluate radiolabeled somatostatin analog scans in the therapeutic workup of carcinoids. Twenty-one patients with carcinoids underwent 26 scans with iodine octreotide or indium pentetreotide. The results for tumor and metastases imaging were analyzed and compared with those of a short inhibition test of marker secretion and with those of metaiodobenzylguanidine scan. The sensitivity for obtaining images of the overall 43 tumor sites was 72%. We had no false-positive results. Unknown tumor sites were discovered in three patients. The results were slightly better with indium pentetreotide and metastases imaging. A positive scan did not always preclude responsiveness to the functional effect of octreotide. Results of somatostatin analog scans were better than those with metaidobenzylguanidine. The two techniques were complementary in one patient. The choice of treatment for patients with carcinoid tumors should benefit from functional inhibition test with octreotide and from indium pentetreotide and metaidobenzylguanidine scans.