68Ga-DOTATOC and 18F-FDG PET/CT for identifying the primary lesions of suspected and metastatic neuroendocrine tumors: A prospective study in Taiwan

Background/purpose: To investigate the diagnostic accuracy of 68Ga-DOTATOC and 18F-FDG PET/CT to identify the primary foci in Taiwanese patients with clinically suspected neuroendocrine tumors (NET) and NET of unknown primary site. Methods: Patients with clinically suspected NET and NET of unknown primary site were eligible. All participants underwent a conventional workup (including CT, MR, endoscopic ultrasound), 68Ga-DOTATOC, and 18F-FDG PET/CT. The results of pathology and findings on clinical follow-up served as the gold standard. Results: Among the 36 patients included in the study, we were able to identify the primary tumor in 17 participants (47.2%). The overall sensitivity values of 68Ga-DOTATOC, 18F-FDG, and conventional workup were 88%, 41%, and 53%, respectively, whereas the specificities were 100%, 100%, 68%, respectively. The areas under curve of 68Ga-DOTATOC, 18F-FDG, and conventional workup were 0.941, 0.706, and 0.607, respectively. 68Ga-DOTATOC was more sensitive than 18F-FDG and more specific than conventional workup. Treatment changes as a result of 68Ga-DOTATOC PET/CT findings occurred in 12 (33.3%) of the 36 study participants. Conclusion: Our data confirm the usefulness of 68Ga-DOTATOC in the identification of NET. In addition, treatment modifications as a result of 68Ga-DOTATOC PET/CT findings were evident in approximately one third of NET patients.