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.