Prognostic value and staging categories of anatomic masticator space involvement in nasopharyngeal carcinoma: a study of 924 cases with MR imaging.
OBJECTIVE
To identify the prognostic value and staging categories of masticator space involvement in nasopharyngeal carcinoma (NPC) as determined with anatomic criteria ("anatomic masticator space involvement") to determine whether it is necessary for the masticator space described with criteria of the American Joint Committee on Cancer to exclude the medial and lateral pterygoid muscles.


METHODS
This retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. NPC was diagnosed in 924 patients with magnetic resonance (MR) imaging, and medical records and imaging studies were retrospectively analyzed. The overall survival, local relapse-free survival, and distant metastasis-free survival of these patients were analyzed by using the Kaplan-Meier method; differences were compared by using the log-rank test.


RESULTS
The frequency of anatomic masticator space involvement was 19.7% (182 of 924 patients). With use of multivariate analysis, anatomic masticator space involvement was identified as an independent prognostic factor for overall survival (P = .02). In addition, anatomic masticator space involvement was associated with a marginally significant decrease in local relapse-free survival (P = .05); however, it had no effect on distant metastasis-free survival. There were no statistically significant differences between different degrees of anatomic masticator space involvement with regard to overall survival and local relapse-free survival in NPC (P = .34 and P = .54, respectively) or between T3 or T4 disease and anatomic masticator space involvement with regard to overall survival and local relapse-free survival (P = .63 and P = .44, respectively).


CONCLUSIONS
Anatomic masticator space involvement affects the overall survival and local relapse-free survival of patients with NPC. When masticator space involvement includes the medial and lateral pterygoid muscles, the disease should be classified as stage T4.
Tang
Ling-Long
LL
State Key Laboratory of Oncology in Southern China and Department of Radiation Oncology, Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, People's Republic of China.
Li
Wen-Fei
WF
Chen
Lei
L
Sun
Ying
Y
Chen
Yong
Y
Liu
Li-Zhi
LZ
Mao
Yan-Ping
YP
Lin
Ai-Hua
AH
Li
Li
L
Ma
Jun
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000473:pathology*; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D011626:Pterygoid Muscles / Q000473:pathology*; D012189:Retrospective Studies; D015996:Survival Rate
D003287:Contrast Media; D019786:Gadolinium DTPA