The role of 111In-Octreotide scintigraphy in the detection of APUD tumours: our experience in eighteen patients.

111In-Octreotide scintigraphy has been recently proposed as a sensitive technique for the detection of neuroendocrine tumours, based on the high radiotracer affinity towards the somatostatin receptors expressed by the APUD-system cells. In the present study, a group of 18 patients with carcinoid tumours and gastrointestinal (GI) apudomas was investigated to assess the accuracy of Octreotide scintigraphy in localizing primitive, recurrent or metastatic lesions. Both planar and SPECT studies were obtained 4 hours after the i.v. injection of 111In-Octreotide (111 MBq); planar images were also carried out 24 hours later. In accordance with other authors, the sensitivity of the method was found to be very high (94%) in our group of patients; only in one case of nesidioblastosis was the scintigraphy negative. No differences in sensitivity were observed between the planar and SPECT studies, but the latter provided a better topographic localization of the neoplastic foci. It should be pointed out that in 7 cases (3 primitive, 1 recurrent and 3 metastatic lesions) scintigraphy correctly localized the tumour, when the other morphological techniques, such as echography, computed tomography or magnetic resonance, failed. On the basis of our data, we believe that Octreotide scintigraphy should be the first study performed in the evaluation of patients affected by APUD tumours.