A new T staging system for nasopharyngeal carcinoma based on intensity-modulated radiation therapy: results from a prospective multicentric clinical study.
OBJECTIVE
This prospective multicentric study aimed to establish a new clinical T staging standard for nasopharyngeal carcinoma (NPC) based on intensity-modulated radiotherapy (IMRT).


METHODS
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.
Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University Nanning 530021, Guangxi, P. R. China.
Min
M
Kang
Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University Nanning 530021, Guangxi, P. R. China.
Pingting
P
Zhou
Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University Nanning 530021, Guangxi, P. R. China.
Tingting
T
Wei
Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University Nanning 530021, Guangxi, P. R. China.
Tingting
T
Zhao
School of Public Health, Guangxi Medical University Nanning 530021, Guangxi, P. R. China.
Jianxiong
J
Long
Department of Radiation Oncology, Liuzhou Worker Hospital Liuzhou 545000, Guangxi, P. R. China.
Guisheng
G
Li
Department of Radiation Oncology, First People's Hospital of Yulin City Yulin 537000, Guangxi, P. R. China.
Haolin
H
Yan
Department of Radiation Oncology, People's Hospital of Guangxi Zhuang Autonomous Region Nanning 530021, Guangxi, P. R. China.
Guosheng
G
Feng
Department of Radiation Oncology, Affiliated Hospital of Guilin Medical University Guilin 541000, Guangxi, P. R. China.
Meilian
M
Liu
Department of Radiation Oncology, Wuzhou Red Cross Hospital Wuzhou 543000, Guangxi, P. R. China.
Jinxian
J
Zhu
Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University Nanning 530021, Guangxi, P. R. China.
Rensheng
R
Wang
Nasopharyngeal carcinoma; T staging; intensity modulated radiation therapy; magnetic resonance imaging; prognosis