ABSTRACT
Objective To establish a new T staging system for nasopharyngeal carcinoma ( NPC) based on magnetic resonances imaging ( MRI) and intensity?modulated radiotherapy ( IMRT) . Methods A retrospective analysis was performed on the clinical data of 608 patients who were newly diagnosed with non?metastatic NPC by MRI and treated with IMRT in our hospital from 2008 to 2010. All patients were staged according to the 7th edition of the UICC/AJCC staging system for NPC. The survival rates were calculated using the Kaplan?Meier method and analyzed using the log?rank test. The Cox regression model was used for multivariate analyses. To deal with the deficiency in the current UICC/AJCC staging system, a new T staging system for NPC was established and systematically evaluated. Results The 5?year follow?up rate was 94?5%. The 5?year overall survival (OS), disease?free survival, local relapse?free survival (LRFS), and distant metastasis?free survival rates were 81?5%, 80?1%, 86?0%, and 81?1%, respectively. The univariate and multivariate analyses showed that the anatomic structures of nasopharynx, parapharyngeal space, and skull base were influencing factors for the OS rate (P=0?000?0?045). New T staging criteria were proposed based on the risk differences and survival curves:stage T1:invasion of the nasopharynx, parapharyngeal space, oropharynx, nasal cavity, skull base, and internal pterygoid muscle;stage T2:invasion of the external pterygoid muscle, paranasal sinus, intracalvarium, infratemporal fossa, and cranial nerves. The proposed T staging system achieved a good separation in both OS and LRFS curves. Conclusions The proposed new T staging system gives an objective prognostic prediction in patients with NPC, which provides an exploratory attempt toward a new clinical staging system for NPC.