title: Staging systems for papillary thyroid carcinoma: a study of 2 tertiary referral centers.
abstract: OBJECTIVE
  To find out the most applicable and consistent staging system for papillary thyroid carcinoma (PTC) available in the literature.
  
  
  BACKGROUND
  The commonly used staging systems for PTC have predicted cancer-specific survival (CSS) well. However, their applicability and generalizability have not yet been evaluated in different clinical settings.
  
  
  METHODS
  A MEDLINE search from 1965 to 2005 was carried out to identify different staging systems available in the literature and 9 systems were applicable to 1634 PTC patients within 2 tertiary-referral centers. The CSS of each staging system within individual centers were calculated using Kaplan-Meier method and the CSS of each tumor stage in one individual center was compared with that of the other by log-rank test. In addition, within each center, the predictability of each staging system relative to the others was ranked based on the proportion of variation explained (PVE) value.
  
  
  RESULTS
  Clinicopathologic features, treatment received, and tumor stages were significantly different between the 2 centers. There were also significant differences in CSS within at least one tumor stage between the 2 centers in 8 of the 9 staging systems. The TNM was a highly predictive and consistent staging system within the 2 centers. Although the absolute PVE values differed between the 2 centers, the relative ranking of the 9 staging systems within each center correlated significantly to each other (P < 0.05).
  
  
  CONCLUSIONS
  Despite referral, treatment, and data collection biases inherent within each center, the TNM system remained to be the most applicable and consistent staging system for PTC in 2 centers managing the same population group.
authors.affiliation: From the *Division of Endocrine Surgery, Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong SAR, China.
authors.forename: Brian Hung-Hin
authors.initials: BH
authors.lastname: Lang
authors.forename: Sin-Ming
authors.initials: SM
authors.lastname: Chow
authors.forename: Chung-Yau
authors.initials: CY
authors.lastname: Lo
authors.forename: Stephen C K
authors.initials: SC
authors.lastname: Law
authors.forename: King-Yin
authors.initials: KY
authors.lastname: Lam
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000401:mortality* / Q000473:pathology*; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000295:instrumentation; D011379:Prognosis; D012017:Referral and Consultation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D013964:Thyroid Neoplasms / Q000401:mortality* / Q000473:pathology*; D013997:Time Factors; D014481:United States / Q000453:epidemiology