title: Combined imaging with 18F-FDG-PET/CT and 111In-labeled octreotide SPECT for evaluation of thymic epithelial tumors.
abstract: OBJECTIVE
  This study aimed to test the role of combined imaging with 18F-FDG-PET/CT and 111In-octreotide SPECT in characterizing thymic epithelial tumors (TETs).
  
  
  METHODS
  We evaluated 20 patients with newly diagnosed TETs who had undergone concomitant 18F-FDG-PET/CT and 111In-octreotide SPECT. Thymic epithelial tumors were classified by World Health Organization (WHO) as low-risk thymomas (5), high-risk thymomas (4), and thymic carcinomas (11, among which 6 neuroendocrine tumors). Patients were staged according to Masaoka system. 18F-FDG-PET/CT was performed and SUV(max) of primary tumors was recorded. 111In-octreotide SPECT of the thorax was performed, and tumor-to-background ratio was determined on the 24-hour coronal sections.
  
  
  RESULTS
  All patients showed increased 18F-FDG uptake in mediastinal lesions. SUV(max) were significantly correlated with WHO classification (r = 0.66, P < 0.01) and with Masaoka stage (r = 0.60, P < 0.01). SUV(max) of low-risk thymomas (mean [SD], 2.87 [0.83]) were significantly lower than those of high-risk thymomas (mean [SD], 7.21 [1.73], P < 0.01) and of thymic carcinomas (mean [SD], 9.39 [5.80], P < 0.05), whereas no significant difference was found between high-risk thymomas and thymic carcinomas. SUV(max) of all high-risk thymomas and thymic carcinomas was 4.5 or greater. All primary tumors were detected by In-octreotide SPECT, and tumor-to-background ratios ranged between 1.67 and 10.10. No statistically significant correlation was found between tumor-to-background ratios and WHO classification (r = 0.24, P = 0.36) and Masaoka stages (r = 0.31, P = 0.23). However tumor-to-background ratios of thymic neuroendocrine tumors (mean [SD], 5.71 [3.09]) were significantly higher than those of all other TETs with SUV(max) of 4.5 or greater (mean [SD], 2.41 [0.56]; P < 0.05).
  
  
  CONCLUSIONS
  18F-FDG-PET/CT scan allows to differentiate high-risk epithelial tumors and thymic carcinomas from low-risk thymomas, whereas 111In-octreotide SPECT may identify neuroendocrine tumors among those showing high 18F-FDG uptake.
authors.affiliation: Department of Biomorphological and Functional Sciences, University of Naples Federico II, Naples, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: De Luca
authors.forename: Rosa
authors.initials: R
authors.lastname: Fonti
authors.forename: Giovannella
authors.initials: G
authors.lastname: Palmieri
authors.forename: Piera
authors.initials: P
authors.lastname: Federico
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Del Prete
authors.forename: Roberto
authors.initials: R
authors.lastname: Pacelli
authors.forename: Leonardo
authors.initials: L
authors.lastname: Pace
authors.forename: Sabino
authors.initials: S
authors.lastname: De Placido
authors.forename: Marco
authors.initials: M
authors.lastname: Salvatore
authors.forename: Silvana
authors.initials: S
authors.lastname: Del Vecchio
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009375:Neoplasms, Glandular and Epithelial / Q000000981:diagnostic imaging*; D015282:Octreotide / Q000031:analogs & derivatives*; D049268:Positron-Emission Tomography; D012372:ROC Curve; D012189:Retrospective Studies; D013953:Thymus Neoplasms / Q000000981:diagnostic imaging*; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
chemical_list: C094279:indium-111-octreotide; D019788:Fluorodeoxyglucose F18; D015282:Octreotide