18 F-FDG PET/CT Nasopharyngeal Abnormal Imaging Analysis And 18 F-NaF PET/CT Evaluation Of Skull Base Bone Invasion And Bone Metastasis In Patients With Nasopharyngeal Carcinoma

Part I Imaging Feature Analysis of abnormal uptake at nasopharyngeal on ¹⁸F-FDG PET/CTObjective: The purpose of this study was to analyze the ¹⁸F-FDG PET/CT images and to evaluate the parameters between benign and malignant lesions of nasopharynx. Method: Our study retrospectively analyzed 149 patients with pathologically proven lesions from October 2010 to December 2015. Patients were divided into four groups: nasopharyngeal carcinoma, lymphoma of nasopharynx, nonspecific inflammation of nasopharynx and the others. Measurement of the nasopharynx's SUVmax, SUVmean and metabolic tumor volume and the cervical lymph nodes' SUVmax were evaluated. In addition, we assessed the morphology of nasopharynx, whether the Waldeyer's ring been involved and the symmetry of cervical lymph nodes. Use independent samples T test, one-way ANOVA test, Chi-Square test and Fisher' exact test were used to compare the differences in PET/CT parameters. Receiver-operating-characteristic curves were applied to evaluate the efficacy. Results: The nasopharynx's SUVmax and SUVmean of nasopharyngeal carcinoma were both higher than those of lymphoma of nasopharynx?P=0.02 and P=0.004? and nonspecific inflammation of nasopharynx?P<0.001 for both?. Metabolic tumor volume showed no significant difference between nasopharyngeal carcinoma and lymphoma of nasopharynx. Nasopharyngeal carcinoma showed symmetry of nasopharynx and Waldeyer's ring involvement less frequent than lymphoma of nasopharynx?P<0.001 and P=0.004?. However, skull base invasion in nasopharyngeal carcinoma was more than lymphoma of nasopharynx and nonspecific inflammation of nasopharynx?P<0.001?. when SUVmax of 8.11 was used as cut off for detection of malignant uptake in nasopharynx, the area under the ROC curve was 0.801±0.054?95% confidence interval, 0.70-0.91?, with a sensitivity of 72.8% and a specificity of 78.3%. The group of the others include four cases, which were nasopharyngeal tuberculosis, Rosai-dorfman disease, nasopharyngeal melanoma and a case with inconsistent three pathological reports. Conclusions: The morphology of nasopharynx, the involvement of skull base, the Waldeyer's ring, and the intensity of ¹⁸F-FDG uptake can provide reliable reference value to differentiate benign from malignant nasopharyngeal abnormal uptake.Part II Comparison of clinic value between ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT in detecting the invasion of skull base and osseous metastases of patients with nasopharyngeal carcinomaObjective:Our study aimed to compare the diagnostic value of ¹⁸F-NaF positron emission tomography-computed tomography?PET/CT? and ¹⁸F-fluorodeoxyglucose?FDG? PET/CT for detection of skull base invasion and osseous metastases in patients with NPC, and then to assess the added value of ¹⁸F-NaF PET/CT. Methods: Our study retrospectively analyzed 45 patients with pathologically proven NPC. They all underwent both ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT within a 7-day interval. Bone metastases were confirmed by follow up using approaches such as enhance-contrast computed tomography?CT? and magnetic resonance image?MRI? and so on. These two examinations were compared using per-patient based analysis and per-lesion based analysis.Results: ¹⁸F-NaF PET/CT detected 27 patients with skull base invasion while ¹⁸F-FDG PET/CT detected 17 positive patients. The sensitivity, specificity, PPV and NPV of ¹⁸F-NaF PET/CT for detecting skull base invasion were 100%, 94.7%, 96.3%, 100%, respectively, whereas for¹⁸F-FDG PET/CT these diagnostic measures were 65.4%, 100%, 100% and 67.9%, respectively. ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT differed significantly in diagnosing skull base invasion?P= 0.02? while the difference in specificity was not significant?P=1?. Osseous metastases were detected in 26 of 45 patients by at least one examination using ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT. ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT detected 208 and 81 bone metastatic lesions, respectively. ¹⁸F-NaF PET/CT detected more metastatic lesions than ¹⁸F-FDG PET/CT?t= 2.287,P= 0.029?. The sensitivity, specificity, PPV and NPV of ¹⁸F-NaF PET/CT for detecting bone metastatic lesions were 98.3%, 65.7%, 97.1% and 88.5%, respectively; these values were 42.0%, 97.1%, 98.6% and 25.2%, respectively, for ¹⁸F-FDG PET/CT. The sensitivity of ¹⁸F-NaF PET/CT in detecting osseous metastases was higher than ¹⁸F-FDG PET/CT?P<0.0001?.Conclusion: In patients with nasopharyngeal carcinoma, ¹⁸F-NaF PET/CT assessed invasion of the skull base better and detected more osseous metastases than ¹⁸F-FDG PET/CT. ¹⁸F-NaF PET/CT had additional value in improving the management.