title: Nasopharyngeal cancer: impact of skull base invasion on patients prognosis and its potential implications on TNM staging.
abstract: OBJECTIVE
  To evaluate patterns of skull base invasion and its possible impact on tumor (T)-staging in nasopharyngeal carcinoma (NPC) using magnetic resonance imaging (MRI).
  
  
  METHODS
  838 consecutive newly diagnosed by biopsy proven and untreated patients with NPC underwent MRI. The skull-base invasion of NPC was classified according to their incidence from proximal sites to more distant sites surrounding the nasopharynx as: high (≥35%), medium (≥5-35%), and low (<5%) groups. A retrospective analysis of data consisting of a 5-year follow-up was carried out. The skull base invasion was related to their tumor (T) staging and prognosis at the 5-year follow-up after treatment with definitive radiation therapy. In addition, a survival health-related quality of life (QOL), overall survival (OS), local relapse-free survival (LRFS) and distant metastasis-free survival (DMFS) were also assessed among the three groups.
  
  
  RESULTS
  The total incidence of skull-base invasion was 65.51% (549/838). The differences in T-stage distribution, and the total survival health-related QOL, among the three groups were statistically significant (χ(2)=160.45, p<0.005; χ(2)=38.43, p<0.005, respectively). The differences between any two of the three groups were also significant, except when the medium grade was compared to the low grade. Significant differences were observed with regard to 5-year OS (83.2%, 74.7%, 59.2%, p=0.000) and DMFS (95.0%, 88.0%, 88.0%, p=0.016); no significant difference was observed in LRFS (95.3%, 95.6%, 91.23%, p=0.450).
  
  
  CONCLUSIONS
  The results indicate that medium and low group displayed similar findings of skull base invasion, and survival status. We, therefore, propose that patients in these two groups be grouped under T4 in the TNM classification that might have a bearing in implementing optimum treatment.
authors.affiliation: Imaging Diagnosis and Interventional Center, State Key Laboratory of Oncology in Southern China, Sun Yat-sen University, Guangzhou 510060, China. liyizhuo68@126.com
authors.forename: Yi-Zhuo
authors.initials: YZ
authors.lastname: Li
authors.forename: Pei-Qiang
authors.initials: PQ
authors.lastname: Cai
authors.forename: Chuan-Miao
authors.initials: CM
authors.lastname: Xie
authors.forename: Zi-Lin
authors.initials: ZL
authors.lastname: Huang
authors.forename: Guo-Yi
authors.initials: GY
authors.lastname: Zhang
authors.forename: Yao-Pan
authors.initials: YP
authors.lastname: Wu
authors.forename: Li-Zhi
authors.initials: LZ
authors.lastname: Liu
authors.forename: Ci-Yong
authors.initials: CY
authors.lastname: Lu
authors.forename: Rui
authors.initials: R
authors.lastname: Zhong
authors.forename: Pei-Hong
authors.initials: PH
authors.lastname: Wu
mesh_terms: D000328:Adult; D000368:Aged; D002681:China / Q000453:epidemiology; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000532:radiotherapy; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging / Q000379:methods; D011379:Prognosis; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D019292:Skull Base Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000517:prevention & control; D016019:Survival Analysis; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult