How Does Magnetic Resonance Imaging Influence Staging According to AJCC Staging System for Nasopharyngeal Carcinoma Compared With Computed Tomography?

Purpose: To analyze the degree and pattern of influence of magnetic resonance imaging (MRI) on staging according to the 6th edition of the American Joint Committee on Cancer staging system compared with computed tomography (CT). Methods and Materials: The MRI and CT scans and medical records of 420 consecutive patients with newly diagnosed nasopharyngeal carcinoma (NPC) were analyzed retrospectively. The tumors of all patients were staged according to the 6th edition of the American Joint Committee on Cancer staging system. Results: A significant difference (p <0.05) was found between CT and MRI in demonstrating involvement in the oropharynx (CT, 25.0% vs. MRI, 14.5%), prevertebral muscle (CT, 18.4% vs. MRI, 36.0%), parapharyngeal space (CT, 82.6% vs. MRI, 68.8%), skull base (CT, 31.0% vs. MRI, 52.6%), sphenoid sinus (CT, 13.6% vs. MRI, 16.7%), ethmoid sinus (CT, 7.1% vs. MRI, 3.3%), intracranial area (CT, 4.8% vs. MRI, 16.0%), and retropharyngeal lymph nodes (CT, 52.1% vs. MRI, 69.0%). The incidence of cervical lymph node metastasis and lymph node metastasis at each level was similar according to CT and MRI. MRI resulted in changes in 49.8% of T stage cases, 10.7% of N stage cases, and 38.6% of clinical stage cases. Conclusion: MRI demonstrated early primary tumor involvement more precisely and deep primary tumor infiltration more easily. The use of MRI caused dramatic changes in the results of the T stage and clinical staging and should be preferred to CT in staging NPC. Patients would benefit from changes in treatment strategies resulting from the use of MRI