Comparison of somatostatin analogue and metaiodobenzylguanidine scintigraphy for the detection of carcinoid tumours.

The purpose of this prospective study was to compare the ability of radiolabelled somatostatin analogue (RSA) and metaiodobenzylguanidine (MIBG) scintigraphy to display carcinoid tumours. Forty patients were studied after radiological assessment based on clinical symptomatology. These patients had radiologically demonstrated tumours (n=28), resected tumours discovered to be of the carcinoid type (n=5) or clinically and biologically suspected carcinoid tumours (n=7). They underwent indium-111 DTPA-pentetreotide or iodine-123-Tyr-3-octreotide and 131I-MIBG scintigraphy. The results were compared with those of complementary surgical or morphological examinations and analysed according to the site of the tumour and the symptomatology. In the case of 31 patients with a total of 55 tumoral sites, the sensitivity of the initial radiological assessment, of RSA and of MIBG was 96%, 86% and 64%, respectively, for the detection of at least one tumour per patient, but 51%, 85% and 51%, respectively, for the total number of sites. No site was detected solely by MIBG. The concordance between RSA and MIBG was better when all sites were considered (kappa index+0.44) than for only extrahepatic abdominal tumoral sites (kappa index+0.095). Abdominal, thoracic or bone marrow tumours were more easily detected with RSA than with MIBG. Hepatic invasion (21 cases) was more easily detected by radiology (sensitivity 100%) than by RSA and MIBG, both of which displayed a sensitivity of 80%, but with differences in uptake intensity. Tumour detection using MIBG was more significantly linked with flush (P<0.01) than with diarrhoea (P>0.10). In the assessment of carcinoid tumours, RSA scintigraphy should be carried out initially (just after hepatic ultrasonography) and supplemented by MIBG, as comparison of the studies serves to guide therapeutic options and might be valuable for prognosis.