A new T staging system for nasopharyngeal carcinoma based on intensity-modulated radiation therapy: results from a prospective multicentric clinical study.

Abstract

PURPOSE: This prospective multicentric study aimed to establish a new clinical T staging standard for nasopharyngeal carcinoma (NPC) based on intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: Between January 2006 and December 2009, four hundred and ninety-two NPC patients undergoing IMRT were staged according to the seventh edition of the UICC/AJCC staging system. The Kaplan-Meier method was used to calculate survival rates, and the log-rank test was used to compare survival differences. RESULTS: The 5-year overall survival (OS), disease-free survival (DFS), recurrence-free survival (RFS), and distant metastasis-free survival (DMSF) rates were 80.5%, 78.6%, 94.1%, and 84.3%, respectively. Univariate and multivariate analyses showed that the invasion of the nasal cavity, parapharyngeal space, oropharynx, skull base, internal pterygoid muscle, external pterygoid muscle, paranasal sinus, infratemporal fossa, orbit, cranial nerves, cavernous sinus, and intracalvarium were independent prognostic factors (P<0.05). According to the results of risk variety and survival curves, we suggest that the new T staging system for NPC based on magnetic resonance imaging and intensity modulated radiation therapy can be classified as T1 (nasopharynx, nasal cavity, parapharyngeal space, oropharynx, skull base and internal pterygoid muscle) and T2 (external pterygoid muscle, paranasal sinus, infratemporal fossa, orbit, cranial nerves, cavernous sinus and intracalvarium). Compared to the seventh edition of UICC/AJCC staging system, our new recommended staging system performs better in risk difference and distribution balance. Furthermore, the differences between the substages of 5-year curves of LRFS, DMFS and OS were all statistically significant in our new recommended staging system. CONCLUSIONS: Our new recommended staging system is more adaptable to IMRT and can predict the prognosis of NPC patient in a more objective and accurate manner.