Combined imaging with 18F-FDG-PET/CT and 111In-labeled octreotide SPECT for evaluation of thymic epithelial tumors

Clin Nucl Med. 2013 May;38(5):354-8. doi: 10.1097/RLU.0b013e318286bd84.


Purpose: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Female
  • Fluorodeoxyglucose F18*
  • Humans
  • Male
  • Middle Aged
  • Multimodal Imaging*
  • Neoplasms, Glandular and Epithelial / diagnostic imaging*
  • Octreotide / analogs & derivatives*
  • Positron-Emission Tomography*
  • ROC Curve
  • Retrospective Studies
  • Thymus Neoplasms / diagnostic imaging*
  • Tomography, Emission-Computed, Single-Photon*
  • Tomography, X-Ray Computed*


  • indium-111-octreotide
  • Fluorodeoxyglucose F18
  • Octreotide

Supplementary concepts

  • Thymic epithelial tumor