title: A new T classification based on masticator space involvement in nasopharyngeal carcinoma: a study of 742 cases with magnetic resonance imaging.
abstract: BACKGROUND
  The aim of this study was to investigate the prognostic significance and various classifications for anatomic masticator space involvement (MSI) in patients with nasopharyngeal carcinoma (NPC).
  
  
  METHODS
  This study retrospectively analyzed 742 patients with untreated nondisseminated NPC who underwent magnetic resonance imaging (MRI) scan of the nasopharynx and neck. The MSI was graded according to different anatomic features. The overall survival (OS), local relapse-free survival (LRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) of the patients with different MSI grades were analyzed using the Kaplan-Meier method and log-rank tests.
  
  
  RESULTS
  The frequency of MSI was 24.1% (179/742). The 5-year OS, LRFS, DMFS, DFS for NPC patients with versus without MSI were 70.9% versus 82.5% (P = 0.001), 94.1% versus 91.4% (P = 0.511), 81.4% versus 88.7% (P = 0.021), and 78.0% versus 83.5% (P = 0.215), respectively. Significant differences in OS were also found among different MSI groups. In the patients with MSI, the OS of the group with medial and/or lateral pterygoid involvement (MLPI) NPC was 73.9% compared to 51.3% (P < 0.0001) in the patients with infratemporal fossa involvement (IFI).
  
  
  CONCLUSIONS
  MSI was an independent prognostic factor for OS and DMFS. NPCs invading the masticator space should be separately categorized into MLPI and IFI prognostic groups. We suggest that MLPI should be staged as T3 while IFI is staged as T4 disease in future TNM staging revision.
authors.forename: Dong-Hua
authors.initials: DH
authors.lastname: Luo
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Hui-Zhi
authors.initials: HZ
authors.lastname: Qiu
authors.forename: Ting
authors.initials: T
authors.lastname: Shen
authors.forename: Qiu-Yan
authors.initials: QY
authors.lastname: Chen
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Huang
authors.forename: Rui
authors.initials: R
authors.lastname: Sun
authors.forename: Chao-Nan
authors.initials: CN
authors.lastname: Qian
authors.forename: Hai-Qiang
authors.initials: HQ
authors.lastname: Mai
authors.forename: Xiang
authors.initials: X
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, PR China. mohy@sysucc.org.cn.
authors.forename: Hao-Yuan
authors.initials: HY
authors.lastname: Mo
mesh_terms: D000328:Adult; D000368:Aged; D002277:Carcinoma; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008410:Masticatory Muscles / Q000473:pathology* / Q000528:radiation effects; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology*; D009367:Neoplasm Staging; D011379:Prognosis; D012189:Retrospective Studies; D055815:Young Adult