title: Prognostic value and staging categories of anatomic masticator space involvement in nasopharyngeal carcinoma: a study of 924 cases with MR imaging.
abstract: 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.
authors.affiliation: 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.
authors.forename: Ling-Long
authors.initials: LL
authors.lastname: Tang
authors.forename: Wen-Fei
authors.initials: WF
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Sun
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Li-Zhi
authors.initials: LZ
authors.lastname: Liu
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Mao
authors.forename: Ai-Hua
authors.initials: AH
authors.lastname: Lin
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
mesh_terms: 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
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA