title: Additional information gained by positron emission tomography with (68)Ga-DOTATOC for suspected unknown primary or recurrent neuroendocrine tumors.
abstract: OBJECTIVE
  Positron emission tomography (PET)/computed tomography (CT) using (68)Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-D-Phe(1)-Tyr(3)-octreotide (DOTATOC) has been used to detect neuroendocrine tumors (NETs). The purpose of this study was to investigate the clinical efficacy of DOTATOC-PET/CT for detecting clinically suspected NETs when conventional imaging modalities were negative or inconclusive, in terms of additional value.
  
  
  METHODS
  A total of 46 patients were analyzed retrospectively. Among them, 14 patients underwent a DOTATOC-PET/CT scan for detecting unknown primary tumors after histopathological confirmation of a NET at metastatic sites (group A): 7 patients for detecting metastasis or recurrence after surgery for NET because of their high hormone levels but with no recurrence detected by other imaging modalities (group B); the remaining 25 patients for detecting suspected NETs because their hormone levels were high with no history of histopathologically proven NET (group C). Additional information was assessed, according to each situation.
  
  
  RESULTS
  In group A, unknown primary tumors were suspected by DOTATOC-PET/CT in 8 of 14 patients (gastrointestinal/pancreatic NET in 7 patients, prostatic cancer in 1 patient), but prostatic cancer was not confirmed by histopathology (i.e., false positive). In group B, DOTATOC-PET/CT depicted lesions in six of seven patients, including nodal metastasis (n = 5) and liver metastasis (n = 1). In group C, DOTATOC-PET/CT did not demonstrate any abnormal foci except in one case of pancreatic NET. Additional information was obtained in 50, 86, and 4 % of cases, in groups A, B, and C, respectively.
  
  
  CONCLUSIONS
  DOTATOC-PET/CT was useful for detecting NETs, especially when recurrence or metastases were suspected because of high hormone levels after surgery for a NET. It is unlikely, however, that additional information can be acquired in patients with no history of NET simply based on high hormone levels.
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoinkawahara-cho, Sakyo-Ku, Kyoto, 606-8507, Japan, ynakamo1@kuhp.kyoto-u.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakamoto
authors.forename: Kohei
authors.initials: K
authors.lastname: Sano
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Ishimori
authors.forename: Masashi
authors.initials: M
authors.lastname: Ueda
authors.forename: Takashi
authors.initials: T
authors.lastname: Temma
authors.forename: Hideo
authors.initials: H
authors.lastname: Saji
authors.forename: Kaori
authors.initials: K
authors.lastname: Togashi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005710:Gallium Radioisotopes; D006728:Hormones / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D015282:Octreotide / Q000031:analogs & derivatives*; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D005710:Gallium Radioisotopes; D006728:Hormones; D019275:Radiopharmaceuticals; D015282:Octreotide; C106246:Edotreotide