Focal Nasopharyngeal Activity Detected on [18F]FDG PET/CT: Clinical Implications and Comparison of Metabolic Parameters for Prediction of Malignancy.

Purpose: We aimed to investigate the incidence and clinical significance of incidental focal nasopharyngeal uptake on [¹⁸F]FDG PET/CT and to evaluate the diagnostic performance of various metabolic parameters to differentiate between benign and malignant nasopharyngeal lesions.

Methods: A total of 63 consecutive patients with incidental focal nasopharyngeal uptake on [¹⁸F]FDG PET/CT and subsequent nasopharyngeal biopsy were retrospectively enrolled. In addition, baseline pretherapeutic [¹⁸F]FDG PET/CT images of 59 patients with newly diagnosed pathologically proven nasopharyngeal carcinoma (NPC) were reviewed. Maximum standardized uptake value (SUVmax), mean SUV (SUVmean), nasopharynx-to-palatine tonsil ratio (NPR), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the nasopharyngeal lesions were determined. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic performance of the metabolic parameters.

Results: Incidental focal nasopharyngeal uptake in two patients (3.2%, 2/63) was pathologically confirmed to be NPC. All the metabolic parameters (SUVmax, SUVmean, NPR, MTV, and TLG) demonstrated significantly greater values in patients with NPC compared with patients with benign or physiological nasopharyngeal uptake (p < 0.001). Among the metabolic parameters, NPR demonstrated the greatest area under the curve of 0.992 (p < 0.05), with a sensitivity of 96.7% and a specificity of 93.4% when a cut-off of 1.1 was used. Similar results were seen in nasopharyngeal lesions without morphological abnormality.

Conclusion: NPC is an infrequent but important cause of incidental focal nasopharyngeal uptake on [¹⁸F]FDG PET/CT. Metabolic parameters were shown to be useful to differentiate between benign and malignant nasopharyngeal lesions, and NPR showed the best diagnostic performance.