title: Prognostic impact of tumor location in stage IV colon cancer: a propensity score analysis in a multicenter study.
abstract: BACKGROUND
  Right-sided colon cancer is considered to be biologically different from left-sided colon cancer; however, conflicting results have been reported regarding differences in prognosis. We aimed to clarify the prognostic impact of tumor location in stage IV colon cancer.
  
  
  METHODS
  Stage IV colon cancer treated from January 1997 to December 2007 (n = 2208) were retrospectively studied. Clinical and pathological features were compared between right-sided colon cancer (cecum, ascending, and transverse colon) and left-sided colon cancer (descending, sigmoid, and rectosigmoid colon). The impact of tumor location on cancer-specific survival (CSS) was analyzed in a multivariate analysis and propensity score analysis to mitigate the differences in background features.
  
  
  RESULTS
  Right-sided colon cancer was associated with older age, female sex, larger tumor size, poorly differentiated adenocarcinoma, mucinous adenocarcinoma, and signet-ring cell carcinoma, a more advanced state within stage IV disease, and a worse CSS. In the cohort matched by propensity scores for background clinicopathological features, tumor location in the right-sided colon was associated with a significantly worse CSS (hazard ratio 1.2, 95% confidence interval 1.1-1.4, p = 0.008) in patients treated with palliative primary tumor resection, but not in those treated with R0 resection or no resection.
  
  
  CONCLUSIONS
  Right-sided colon cancer were diagnosed at a more advanced state within stage IV disease and showed a significantly worse prognosis than left-sided colon cancer, suggesting that stage IV right-sided colon cancer is oncologically more aggressive than left-sided colon cancer.
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Electronic address: ishihara-1su@h.u-tokyo.ac.jp.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Ishihara
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishikawa
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Tanaka
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Tomomichi
authors.initials: T
authors.lastname: Kiyomatsu
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Kazushige
authors.initials: K
authors.lastname: Kawai
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Hata
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Hioaki
authors.initials: H
authors.lastname: Nozawa
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Kanazawa
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kazama
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamaguchi
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Sunami
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Joji
authors.initials: J
authors.lastname: Kitayama
authors.affiliation: Department of Surgery, Teikyo University, 2-11-1, Kaga, Itabashi-ku, Tokyo 173-8605, Japan.
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Hashiguchi
authors.affiliation: Department of Surgical Oncology, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sugihara
authors.affiliation: Department of Surgical Oncology, University of Tokyo Hospital, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Electronic address: toshwatanabe@yahoo.co.jp.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D000230:Adenocarcinoma / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D003110:Colonic Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D011379:Prognosis; D057216:Propensity Score; D016016:Proportional Hazards Models; D012189:Retrospective Studies
keywords: Colon cancer; Prognostic factor; Stage IV; Tumor location