Skip Navigation LinksHome > May 2013 - Volume 38 - Issue 5 > Combined Imaging With 18F-FDG-PET/CT and 111In-Labeled Octre...
Clinical Nuclear Medicine:
doi: 10.1097/RLU.0b013e318286bd84
Original Articles

Combined Imaging With 18F-FDG-PET/CT and 111In-Labeled Octreotide SPECT for Evaluation of Thymic Epithelial Tumors

De Luca, Serena MD*; Fonti, Rosa MD, PhD; Palmieri, Giovannella MD‡§; Federico, Piera MD‡§; Del Prete, Giuseppina MD*; Pacelli, Roberto MD*; Pace, Leonardo MD; De Placido, Sabino MD‡§; Salvatore, Marco MD*†; Del Vecchio, Silvana MD*†§

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Abstract

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 SUVmax 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. SUVmax were significantly correlated with WHO classification (r = 0.66, P < 0.01) and with Masaoka stage (r = 0.60, P < 0.01). SUVmax 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. SUVmax of all high-risk thymomas and thymic carcinomas was 4.5 or greater. All primary tumors were detected by 111In-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 SUVmax 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.

© 2013 by Lippincott Williams & Wilkins

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