Clinical significance of asymmetric 18F-FDG uptake in discriminating retropharyngeal involvement of malignancy from benign lesion

Abstract

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Objectives: While retropharyngeal space is a potential area for involvement of primary or metastatic tumors, its 18F-FDG uptake could be high without malignant involvement. In this study, we evaluated the clinical significance of asymmetric 18F-FDG uptake of retropharyngeal space in cancer patients.

Methods: Forty-six patients (male/female=23/23, age=50±15) who had asymmetric retropharyngeal 18F-FDG uptake by visual analysis were retrospectively. Lesions were divided into 2 groups according to the follow-up study results; Benign or Malignant. Difference (dSUV) and ratio (rSUV) of retropharyngeal 18F-FDG uptake were compared between 2 groups and ROC analysis was performed to choose cut-off values for malignancy.

Results: There were 22 benign and 24 malignant lesions. The most common type of primary cancer was lymphoma (16/46, 35%), and nasopharyngeal caner (12/46, 26%). Both dSUV and rSUV were significantly higher in malignant than benign lesions (8.8 vs. 2.3, p<0.01 for dSUV and 4.7 vs. 2.0, p<0.01 for rSUV). Cut-off values for dSUV and rSUV were 2.6 (AUC= 0.844 ± 0.059) and 2.2 (AUC= 0.780 ± 0.068), and their sensitivity/specificity were 82%/81% and 70%/86%, respectively.

Conclusions: In our study, malignant lesions showed more asymmetric 18F-FDG uptake than benign, and both difference and the ratio of retropharyngeal 18F-FDG uptake could be useful in discriminating the involvement of malignancy from benign lesions.