title: The survival difference between gastric cancer patients from the UK and Japan remains after weighted propensity score analysis considering all background factors.
abstract: BACKGROUND
  Previous studies comparing survival between gastric cancer (GC) patients from the West and the East were based on the assumption that background factors and prognostic factors were identical. The aim of the current study was to compare the survival of GC patients from the UK and Japan using weighted propensity score analysis after identifying all different background factors.
  
  
  METHODS
  Data from 464 patients from the Leeds Teaching Hospital NHS Trust, Leeds, UK (LTHT), and 465 patients from the Kanagawa Cancer Center Hospital, Yokohama, Japan (KCCH), who had surgery for GC were analyzed. Prognostic factors for overall survival (OS) and cancer-specific survival (CSS) were identified by univariate and multivariate analyses. Survival was compared by propensity score weighting after adjusting for all significantly different background factors.
  
  
  RESULTS
  Most background factors were different between LTHT and KCCH patients. Unadjusted stage-specific OS and CSS were significantly better in KCCH. Independent prognostic factors for unadjusted OS and CSS were pT and pN in KCCH and in addition tumor location, pancreatectomy, resection margin status and number of examined lymph nodes in LTHT. Even after adjusting for all background characteristics, survival remained better in KCCH.
  
  
  CONCLUSIONS
  These results suggest that differences in background factors are unable to fully explain the survival difference of GC patients between UK and Japan. Comprehensive studies into the biology of GC and/or host factors are needed to fully understand the survival difference.
authors.affiliation: Department of Gastrointestinal Surgery, Kanagawa Cancer Center, 2-3-2 Nakao, Asahi-ku, Yokohama, Kanagawa, Japan.
authors.forename: Takanobu
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Department of Gastrointestinal Surgery, Kanagawa Cancer Center, 2-3-2 Nakao, Asahi-ku, Yokohama, Kanagawa, Japan. yoshikawat@kcch.jp.
authors.forename: Takaki
authors.initials: T
authors.lastname: Yoshikawa
authors.affiliation: Department of Biostatistics and Epidemiology, Graduate School of Medicine, Yokohama City University, 4-57 Urafune, MInami-ku, Yokohama, Kanagawa, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Taguri
authors.affiliation: Department of Gastrointestinal Surgery, Kanagawa Cancer Center, 2-3-2 Nakao, Asahi-ku, Yokohama, Kanagawa, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Department of Gastrointestinal Surgery, Kanagawa Cancer Center, 2-3-2 Nakao, Asahi-ku, Yokohama, Kanagawa, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Aoyama
authors.affiliation: Department of Upper Gastrointestinal Surgery, Leeds Teaching Hospital NHS Trust, St James's Institute of Oncology, Bexley Wing, St James's University Hospital, Leeds, UK.
authors.forename: Henry M
authors.initials: HM
authors.lastname: Sue-Ling
authors.affiliation: Department of Radiology, Newcastle upon Tyne Hospitals NHS Trust, Newcastle, UK.|Section of Pathology and Tumor Biology, Leeds Institute of Cancer and Pathology, University of Leeds, Leeds, UK.
authors.forename: Kiran
authors.initials: K
authors.lastname: Bonam
authors.affiliation: Department of Upper Gastrointestinal Surgery, Leeds Teaching Hospital NHS Trust, St James's Institute of Oncology, Bexley Wing, St James's University Hospital, Leeds, UK.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Hayden
authors.affiliation: Department of Pathology, Maastricht University Medical Center, P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands. H.Grabsch@maastrichtuniversity.nl.
authors.forename: Heike I
authors.initials: HI
authors.lastname: Grabsch
mesh_terms: D000368:Aged; D005260:Female; D005743:Gastrectomy / Q000706:statistics & numerical data; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010180:Pancreatectomy / Q000706:statistics & numerical data; D011379:Prognosis; D057216:Propensity Score; D013156:Splenectomy / Q000706:statistics & numerical data; D013274:Stomach Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000601:surgery; D016019:Survival Analysis; D006113:United Kingdom / Q000453:epidemiology
keywords: East versus West; Gastric cancer; Prognosis; Propensity score weighting