title: Lesion-based analysis of (18)F-FDG uptake and (111)In-Pentetreotide uptake by neuroendocrine tumors.
abstract: OBJECTIVE
  To characterize the heterogeneity of metastatic neuroendocrine tumor (NET) lesions, we compared the [(18)F]-fluorodeoxyglucose (FDG) uptake and the (111)In-pentetreotide (SRS) uptake for somatostatin receptor scintigraphy using the CT-based fusion imaging techniques of PET/CT and SPECT/CT.
  
  
  METHODS
  Fifteen consecutive patients with NET lesions were examined using both FDG-PET/CT and SRS SPECT/CT prospectively. A total of 45 metastatic NET lesions were evaluated for FDG uptake according to the standardized uptake value (SUV) and for SRS uptake according to the tumor-to-muscle count ratio (T/M ratio); these values were then compared according to the grade of NET (G), also compared to the tumor volume.
  
  
  RESULTS
  Both the SRS uptake and FDG uptake showed no significant correlation to the tumor volume, and suggested no significant artifacts in these data. The T/M ratio for the SRS uptake ranged from 192.7 to 1.9 and exhibited very wide range of distribution. The SUV for the FDG uptake ranged from 13.8 to 0.77 and exhibited narrow range of distribution. The uptake of the two tracers in individual lesions showed an inverse correlation. The G1 + 2 lesions had a higher SRS uptake than the G3 lesions, but the difference was not significant because of the large variation (40.65 ± 48.03, n = 39 vs. 8.66 ± 13.13, n = 6). However, the G1 + 2 lesions had a significantly lower FDG uptake than the G3 lesions (3.52 ± 1.84, n = 39 vs. 10.82 ± 4.50, n = 6). The tracer uptakes varied largely not only in an inter-subject manner, but also in an intra-subject manner.
  
  
  CONCLUSIONS
  An inverse correlation between SRS uptake and FDG uptake in the metastatic NET lesions observed in this study may be consistent with the opposing ideas of differentiation and proliferation in oncology. The large variations in SRS and FDG uptake by metastatic NET lesions suggest the biological heterogeneity of advanced NET. These results support the idea that combination therapy targeting both receptor-positive cells and proliferating cells may be beneficial from a functional imaging perspective.
authors.affiliation: Division of Nuclear Medicine, Department of Radiology, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655, Japan, kkubota@cpost.plala.or.jp.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kubota
authors.forename: Momoko
authors.initials: M
authors.lastname: Okasaki
authors.forename: Ryogo
authors.initials: R
authors.lastname: Minamimoto
authors.forename: Yoko
authors.initials: Y
authors.lastname: Miyata
authors.forename: Miyako
authors.initials: M
authors.lastname: Morooka
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakajima
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000556:secondary; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009132:Muscles / Q000000981:diagnostic imaging / Q000378:metabolism; D060787:Neoplasm Grading; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin / Q000378:metabolism; D013004:Somatostatin / Q000031:analogs & derivatives*; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D019788:Fluorodeoxyglucose F18; D013004:Somatostatin; C081788:pentetreotide