Influence of MRI on the staging system of 78 patients with nasopharyngeal carcinoma (NPC)

Background and purpose: The patients with nasopharyngeal carcinoma(NPC) are staged according to Chinese 1992 staging system that is mainly based on clinical symptoms and CT image.Since MRI has been widely used in the clinic,the results were reported to be more accurate than the CT scan.The purpose of this study was to compare the diversity in tumor extension of NPC by computerized tomography(CT) versus magnetic resonance imaging(MRI) and to evaluate if the difference has any impacts on the '92 staging system.Methods:The MRI and CT were taken and compared prior to radiotherapy for 78 cases with histologically proved NPC from Aug.2005 to Aug.2006.Clinical staging was estimated according to '92 staging system based on both of CT or MRI data and clinical information.Results:MRI was significantly superior to CT in the detection of invasion in anterior-styloid space(82.0% vs 65.4%),oropharynx(34.6% vs 20.5%),retropharyngeal lymphatic metastasis(74.4% vs 55.1%),base of skull(51.3% vs 30.8%),cavernous sinus(19.2% vs 5.1%),nasal sinuses(33.3% vs 19.2%) and pterygopalatine fossa(16.7% vs 6.4%.),all the difference showed statistical significance.There were no statistical differences between CT and MRI in the evaluation of involvement of nasal cavity(28.2% vs 21.8%),post-styloid space(65.4% vs 67.9%),pharynx cavity(2.6% vs 1.3%) and cervical lymph node metastasis.According to MRI data,42.3% of T classification,25.6% of N classification,and 28.2% of clinical stages were changed compared to CT scan.Conclusions:There is remarkable advantage of MRI in the detection of infiltration of NPC,especially in the base of skull,cavernous sinus,and retropharyngeal lymphatic metastasis.The '92 stage system should be changed to adapt MRI information into clinical stage and it might impact on the prognosis of NPC.