Whole-body C-5-hydroxytryptophan positron emission tomography as a universal imaging technique for neuroendocrine tumors – comparison with somatostatin receptor scintigraphy and computed tomography

Neuroendocrine tumors (NET ́s) can be small and situated almost anywhere throughout the body. Our objective was to investigate if whole body (WB) positron emission tomography (PET) with C-5-hydroxytryptophan (5-HTP) can be used as a universal imaging technique for NET ́s and to compare this technique with established imaging methods. Forty two consecutive patients with evidence of NET and a detected lesion on any conventional imaging (6 bronchial-, 2 foregut-, 16 midgut-, and 2 thymic carcinoids, 1 ectopic Cushing ́s syndrome, 4 gastrinomas, 1 insulinoma, 6 non-functioning endocrine pancreatic tumors, 1 gastric carcinoid, 1 paraganglioma and 2 endocrine differentiated pancreatic carcinomas) were studied. The WB-C-5-HTP-PET examinations were compared with WB-computed tomography (CT) and somatostatin receptor scintigraphy (SRS). Tumor lesions were imaged with PET in 95 % of the patients. In 58 % of the patients PET could detect more lesions than SRS and CT, equal numbers in 34 % whereas in 3 cases SRS or CT showed more lesions. In 84% (16/19 patients) PET could visualize the primary tumor compared to 47 % and 42% for SRS and CT respectively. The surgically removed PET-positive primary tumor sizes were 6-30 mm. To conclude, this study indicates that WB-C-HTP-PET can be used as a universal imaging method for detection of NET ́s. This study also shows that WB-C-HTP-PET is sensitive in imaging small NET-lesions, such as primary tumors, and can in a majority of cases image significantly more tumor lesions than SRS and CT.