Comparison of 18F-NaF PET/CT and 18F-FDG PET/CT for Detection of Skull-Base Invasion and Osseous Metastases in Nasopharyngeal Carcinoma

Abstract

Our study aimed at comparing 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 nasopharyngeal carcinoma (NPC). 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 PET/CT, enhance-contrast computed tomography (CT), and magnetic resonance image (MRI). These two examinations were compared using per-patient-based analysis and per-lesion-based analysis. ¹⁸F-NaF PET/CT detected 27 patients with skull-base invasion, whereas ¹⁸F-FDG PET/CT detected 17 patients. ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT differed significantly in diagnosing skull-base invasion (p=0.02) and sensitivity (p=0.008). The sensitivity, specificity, and agreement rate of ¹⁸F-NaF PET/CT for detecting bone metastatic lesions were 98.3%, 65.7%, and 92.9%, respectively; these values were 42.9%, 97.1%, and 51.9%, respectively, for ¹⁸F-FDG PET/CT. ¹⁸F-NaF PET/CT and ¹⁸F-FDG PET/CT differed significantly in the number of osseous metastases detected (t=2.45, p=0.18) sensitivity (p < 0.0001) and specificity (p=0.003). 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.

Figure 1

A 63-year-old man was diagnosed with nonkeratinizing nasopharyngeal carcinoma. (A–C) transverse sections of PET, CT, and fusion views in ¹⁸F-FDG PET/CT, respectively. (D–F) transverse sections of PET, CT, and fusion views in ¹⁸F-NaF PET/CT. (G and H) the maximum intensity projection (MIP) of ¹⁸F-FDG PET/CT and ¹⁸F-NaF PET/CT, respectively. Skull-base invasion was revealed on ¹⁸F-NaF PET/CT but was hidden on ¹⁸F-FDG PET/CT because of the interference from the tumor tissue. This was consistent with MRI two days before ¹⁸F-NaF PET/CT.

Figure 2

A, D, and G are parts of ¹⁸F-FDG PET/CT and C, F, and H are parts of ¹⁸F-NaF PET/CT. B and E are transverse sections of low-dose CT. Abnormal uptake of ¹⁸F-NaF is shown at the right rib and right ilium, whereas no abnormal concentration of ¹⁸F-FDG is found (arrows). The lesions are verified as osseous metastases by CT follow-up.