Background and objective: The 2008 staging system of nasopharyngeal carcinoma (NPC) was generated based on the NPC 92 and AJCC staging system. It remains open to be consummated. This study was to evaluate its rationality as well as compare the stage distribution among the 3 staging systems, by using of MRI imaging.
Methods: MRI data was collected from a cohort of 177 cases of untreated NPC for retrospective review. We accepted the nasal involvement criteria of 2008 staging system, in which the borderline between the nasal cavity and nasopharynx was a line linked between both posterior walls of the maxillary sinus, for all of the 3 systems.
Results: Involvement of oropharynx, nasopharynx, soft palatine, prevertebral muscles, post-styloid space, intracranial, orbit, 1st and/or 2nd cervical body are 100% accompanied with other same or more advanced T-stage classifications. The same situations happened in more than 95% of involvement of the medial pterygoid muscle or masticator space beyond it. Cervical lymph node metastasis (LNM) accounted for 76.3%. Proportion of metastatic lymph node extracapsular extension (ECE) and/or bilateral neck LNM elevated as maximum diameter of the node increased, no matter transverse or longitudinal. There were 11 cases of parotid LNM in this group. Advanced stage accounted for 81.4%, 78.5% and 75.7% in 2008, UICC and NPC 92 staging system, respectively, without statistic difference.
Conclusion: Nasal involvement criteria and T-stage classification of the medial pterygoid muscle defined by NPC 2008 staging system seems reasonable. Stage distribution is also similar to the other 2 systems. However, diameter of the LNM might not be a prognostic factor. Parameters such as how to classify a parotid LNM, or a node which occupies more than one region, require further clarify.