Purpose: At all stages of the disease, serious difficulties are encountered in the imaging diagnosis of carcinoids. Somatostatin receptor scintigraphy (SRS) holds great promise for detecting primary tumours and metastases. 99mTc-EDDA/HYNIC-octreotate should significantly improve the diagnosis of carcinoids in comparison with 111In-Octreoscan owing to the better affinity for SSR2 and the higher count rate. The aim of this study was to assess the diagnostic efficiency of 99mTc-EDDA/HYNIC-octreotate scintigraphy in the detection and staging of carcinoid tumours.
Methods: The study population comprised 75 patients (age 48.5+/-15.5 years): 46 with histological confirmation of carcinoid and 29 with suspected disease. 99mTc-EDDA/HYNIC-octreotate (740 MBq) SRS and CT were performed in all patients. Fifteen patients were examined with 111In-Octreoscan.
Results: High-quality 99mTc-EDDA/HYNIC-octreotate images were obtained in all cases, with maximum tumour tracer accumulation 4 h p.i. The mean target/non-target ratios for whole body (WB) and SPECT scans were, respectively, as follows: primary lesions: 4.5 and 10.2; metastases: liver, 3.1 and 12.3; abdominal focal lesions, 2.7 and 5.8; lung, 2.7 and 8.3; mediastinum, 3.4 and 7.6; bones, 6.8 and 19.0. 99mTc-EDDA/HYNIC-octreotate WB scans revealed more metastases than 111In-Octreoscan, with better individual separation. 99mTc-EDDA/HYNIC-octreotate SRS revealed new metastatic lesions in seven patients with confirmed carcinoid, and in four with dissemination the primary focus was found. Five patients qualified for radioguided surgery and 11 were referred to 90Y-DOTA-TATE therapy. The sensitivity of SRS in comparison with CT was higher for primary lesions and liver and abdominal lymph node metastases. In the subgroup of patients with suspected neuroendocrine tumours, two duodenal carcinoids, one thymic carcinoid and one ileal carcinoid were found.
Conclusion: 99mTc-EDDA/HYNIC-octreotate, with high imaging quality, is an excellent alternative to 111In-Octreoscan for staging of carcinoids, and it seems to be the method of choice for detection of the primary focus in patients with metastases from an unknown primary tumour.