title: The superiority of the seventh edition of the TNM classification depends on the overall survival of the patient cohort: comparative analysis of the sixth and seventh TNM editions in patients with gastric cancer from Japan and the United Kingdom.
abstract: BACKGROUND
  The objective of this study was to investigate whether the seventh edition of the American Joint Committee on Cancer/International Union Against Cancer TNM classification (TNM7) had superior discriminatory ability over the sixth edition of the TNM classification (TNM6) in patients with gastric cancer regardless of their country of origin.
  
  
  METHODS
  In total, 538 patients from the Kanagawa Cancer Center Hospital (Yokohama, Japan) (KCCH) and 519 patients from the Leeds Teaching Hospitals National Health Service Trust (Leeds, United Kingdom) (LTHT) who underwent surgery for gastric cancer were selected. Overall survival was used for statistical analysis. Hazard ratios (HRs) were estimated with disease stage as a continuous variable to evaluate the discriminatory ability of the TNM stage groups. The estimates of log HRs (logHRs) for the TNM6 and the TNM7 stage groups were compared.
  
  
  RESULTS
  In the KCCH cohort, 82 patients (15%) were upstaged, and 26 patients (5%) were downstaged between TNM6 and TNM7 compared with 253 patients (49%) and 53 patients (10%), respectively, in the LTHT cohort. The logHRs for a 1-stage increase within TNM6 and TNM7 were 1.06 and 1.16, respectively, in the KCCH cohort and 0.57 and 0.79, respectively, in the LTHT cohort. The differences in logHRs between TNM6 and TNM7 were significant in each cohort (KCCH: logHR, 0.11; P = .024; LTHT: logHR, 0.21; P = .0002) and between the 2 cohorts.
  
  
  CONCLUSIONS
  TNM7 had superior discriminatory ability compared with TNM6 in both cohorts. The improved ability to discriminate patients with different survival probability when using TNM7 was greater in the LTHT cohort. The current findings indicated that the discriminatory ability of the TNM stage groups may depend on the baseline survival characteristics of the patient cohort.
authors.affiliation: Department of Gastrointestinal Surgery, Kanagawa Cancer Center, Yokohama, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Hayashi
authors.forename: Takaki
authors.initials: T
authors.lastname: Yoshikawa
authors.forename: Kiran
authors.initials: K
authors.lastname: Bonam
authors.forename: Henry M
authors.initials: HM
authors.lastname: Sue-Ling
authors.forename: Masataka
authors.initials: M
authors.lastname: Taguri
authors.forename: Satoshi
authors.initials: S
authors.lastname: Morita
authors.forename: Akira
authors.initials: A
authors.lastname: Tsuburaya
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Hayden
authors.forename: Heike I
authors.initials: HI
authors.lastname: Grabsch
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D013274:Stomach Neoplasms / Q000145:classification* / Q000401:mortality / Q000473:pathology; D006113:United Kingdom