This single-center prospective observational study aims to evaluate the feasibility, cost-effectiveness, and clinical value of positron emission tomography/magnetic resonance imaging (PET/MRI) for initial staging in patients with locally advanced nasopharyngeal carcinoma (NPC). It will compare the diagnostic performance of PET/MRI, including sensitivity, specificity, and staging accuracy, with traditional staging methods such as positron emission tomography/computed tomography (PET/CT).

Nasopharyngeal carcinoma is prevalent in Southeast Asia and North Africa, with approximately 5% of newly diagnosed cases presenting with distant metastases. For patients with N2-3 disease and elevated Epstein-Barr virus (EBV) DNA levels, the risk of distant metastasis can reach 27.5%. Accurate detection of distant metastases at diagnosis is crucial for staging and treatment planning. Current National Comprehensive Cancer Network (NCCN) guidelines recommend fluorodeoxyglucose (18F-FDG) PET/CT for staging in locally advanced nasopharyngeal carcinoma, as traditional tools (e.g., chest CT, abdominal ultrasound, bone scans) may yield false-negative results.

PET/MRI, as a novel imaging technique, offers potential advantages such as improved diagnostic accuracy, shorter scan times, and reduced false-positive rates. However, its clinical application is limited by high costs and equipment availability. This study will explore the clinical value and economic feasibility of PET/MRI in nasopharyngeal carcinoma staging, aiming to establish its potential role in improving diagnostic pathways.

1. Background:

   Nasopharyngeal carcinoma (NPC) is prevalent in Southeast Asia and North Africa, with 5% of newly diagnosed cases showing distant metastases. For N2-3 stage patients with high Epstein-Barr virus (EBV) DNA levels, the metastasis rate can reach 27.5%. Accurate detection at diagnosis is crucial for staging and treatment planning. While the National Comprehensive Cancer Network (NCCN) recommends fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for staging locally advanced NPC, traditional methods like chest CT or ultrasound may yield false negatives. PET/MRI offers improved accuracy and reduced false positives but is limited by high costs and low accessibility. This study examines the cost-effectiveness and clinical value of PET/MRI in NPC staging.

2. Material and methods:

   This study is a single-center prospective observational study. It will recruit patients aged 18 years or older with pathologically confirmed nasopharyngeal carcinoma (NPC) who have not received any NPC-related treatment and agree to participate. All participants will undergo PET/CT and PET/MRI to compare their diagnostic performance in detecting distant metastases, including sensitivity, specificity, and staging accuracy. The study will also evaluate the time efficiency and cost-effectiveness of PET/MRI to explore its clinical value and limitations.

3. Expecting Results:

This study aims to demonstrate that PET/MRI has superior diagnostic accuracy over PET/CT in staging locally advanced nasopharyngeal carcinoma, especially in detecting distant metastases. Despite higher costs, PET/MRI's accuracy may streamline diagnosis, reduce unnecessary tests, and support precise treatment strategies, improving patient outcomes and quality of life. The results will provide evidence for its clinical use and guide future diagnostic improvements.

Inclusion Criteria:

• Pathologically diagnosed with nasopharyngeal carcinoma (NPC) through endoscopic biopsy at the hospital's otolaryngology department.
• Clinically staged as cT3-4/N2-N3.
• Age: 18 years and older.
• Participants must voluntarily sign an informed consent form, acknowledging understanding of the study objectives and potential risks.

Exclusion Criteria:

• Patients with poorly controlled diabetes. -Patients with a history of head and neck malignancies or a history of non- head and neck cancers with no evidence of disease for at least 3 years.
• Patients with clinical staging of cT1-2N0-1.
• Patients with factors that may affect PET/MRI image quality, such as implanted metal devices or MRI contraindications, or those with a history of contrast agent allergies.

The participants in this study are pathologically diagnosed nasopharyngeal carcinoma (NPC) patients, primarily focusing on those with locally advanced staging (cT3-4/N2-N3), who have not yet received any treatment related to NPC. Participants must be 18 years or older, in good physical condition, and able to cooperate in completing imaging examinations and treatments.