18F-NaF uptake in skull-base bone as a predictor of treatment response in advanced nasopharyngeal carcinoma

Abstract

This study investigates the utility of ¹⁸F-sodium fluoride (¹⁸F-NaF) positron emission tomography/computed tomography (PET/CT) in assessing skull-base bone invasion (SBBI) and predicting treatment response in advanced nasopharyngeal carcinoma (NPC). A retrospective analysis was conducted on 142 patients with newly diagnosed advanced NPC who underwent ¹⁸F-NaF PET/CT for initial staging from December 2020 to December 2023. ¹⁸F-NaF PET/CT scans were analyzed for uptake values at the skull-base bone, and these were correlated with treatment outcomes of primary tumor using the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. Statistical analyses involved Mann-Whitney U tests for group comparisons and logistic regression for evaluating risk factors. Higher ¹⁸F-NaF uptake at the skull-base bone was significantly associated with advanced T stages (p < 0.0001) and the presence of bone metastases (p = 0.01). Patients exhibiting complete response (CR) to treatment had significantly lower skull-base ¹⁸F-NaF uptake compared to those with non-CR (p < 0.001). Receiver operating characteristic (ROC) analysis identified an SUV_max > 10.0 and SUV_mean > 5.2 as predictive of non-CR, with AUC values of 0.77 and 0.76, respectively. Univariate and multivariable analysis confirmed SUV_max as a significant predictor of treatment response (OR = 7.03, 95% CI: 1.97-25.13, p < 0.05). Elevated ¹⁸F-NaF uptake at the skull-base bone is predictive of poorer treatment outcomes, highlighting its potential as a prognostic biomarker in advanced NPC. This study demonstrates that ¹⁸F-NaF PET/CT is a valuable imaging modality for evaluating SBBI in NPC, offering metabolic information that complements the anatomical findings from MRI.

Keywords: 18F-NaF; Nasopharyngeal carcinoma; PET/CT; Skull-base bone invasion; Treatment response.

Fig. 1

The flowchart of this study.

Fig. 2

Distribution of ¹⁸F-NaF Uptake at Skull Base Across Tumor Stages in Patients with advanced NPC. (A) The SUV_max for each stage. (B) The SUV_mean for each stage. (C) SBR for each stage. Each data point represents an individual patient measurement, overlaid on bars indicating the median value per stage.

Fig. 3

A 57-y-old man with newly diagnosed locally advanced nasopharyngeal carcinoma who underwent ¹⁸F-NaF PET/CT and MRI at pre-treatment and MRI at post-treatment. (A) Maximum-intensity projection (MIP) and Axial images from ¹⁸F-NaF PET/CT: MIP illustrates a tracer accumulation at the base of the skull (red dashed arrow). Axial images demonstrate high ¹⁸F-NaF uptake in the lesion (dashed circle), with a SUV_max of 7.9. (B) Pre-treatment MRI: Axial contrast-enhanced T1-weighted MRI reveals an enhancing mass at the nasopharyngeal mass associated with bone invasion and soft-tissue extension. (C) Post-treatment MRI: Axial contrast-enhanced T1-weighted MRI taken after therapy shows significant reduction in the size, indicating a complete response to treatment.

Fig. 4

A 37-year-old man with newly diagnosed locally advanced nasopharyngeal carcinoma who underwent ¹⁸F-NaF PET/CT and MRI at pre-treatment and MRI at post-treatment. (A) Maximum-intensity projection (MIP) and Axial images from ¹⁸F-NaF PET/CT: MIP image from an ¹⁸F-NaF PET/CT scan demonstrating a hypermetabolic lesion in the skull base (red dashed arrow). Axial images demonstrate high ¹⁸F-NaF uptake in the lesion (red dashed circle), with a SUV_max of 41.1. (B) Pre-treatment MRI: Axial contrast-enhanced T1-weighted MRI reveals an enhancing mass at the nasopharyngeal mass associated with bone invasion and soft-tissue extension. (C) Post-treatment MRI: Axial contrast-enhanced T1-weighted MRI taken after therapy shows no significant reduction in the size, indicating a stable disease after treatment.

Fig. 5

ROC Curves of ¹⁸F-NaF uptake for predicting non-CR response to treatment.