[Influences of magnetic resonance imaging on the staging system of nasopharyngeal carcinoma].

Background & Objective: The value of magnetic resonance imaging (MRI) in assessing the extension of nasopharyngeal carcinoma (NPC) is better than that of computed tomography (CT). This study was to analyze the influences of MRI on the Chinese '92 staging system and the 6(th) edition International Union Against Cancer/American Joint Committee on Cancer (UICC/AJCC) staging system of NPC.
Methods: From Jan. 2003 to Jun. 2004, 250 naive patients with histologically diagnosed NPC, with no metastasis, received both enhanced spiral CT and MRI scans of the nasopharynx and cervix. Clinical stage was classified according to the Chinese '92 staging system and the 6(th) edition UICC/AJCC staging system, respectively, based on both CT/MRI imaging data and clinical information.
Results: MRI was better than CT in detecting the invasion of NPC in the extra-nasopharyngeal cavity (the oropharyrnx, nasal cavity, and parapharyngeal spatium), retropharyngeal lymph node, base of skull, paranasal sinuses, intracranial cavernous sinus, infratemporal fossa, and cervical vertebra. There was no statistical difference between CT and MRI in detecting cervical lymph node metastasis. Compared with CT, MRI made changes in 32.0% of T stage (including 26.0% up-staging and 6.0% down-staging), 11.6% of N stage (6.4% up-staging and 5.2% down-staging), and 30.4% of clinical stage (24.0% up-staging and 6.4% down-staging) for the Chinese '92 staging system, while made changes in 39.6% of T stage (36.0% up-staging and 3.6% down-staging), 9.2% of N stage (5.6% up-staging and 3.6% down-staging), and 37.6% of clinical stage (33.6% up-staging and 4.0% down-staging) for the 6(th) edition UICC/AJCC staging system.
Conclusions: Compared with CT, MRI has a remarkable advantage in detecting the primary tumor extension of NPC, but has no advantage in detecting cervical lymph node metastasis. It is necessary and feasible to establish a new clinical staging system of NPC based on MRI.