title: Better survival in right-sided versus left-sided stage I - III colon cancer patients.
abstract: The distinction between right-sided and left-sided colon cancer has recently received considerable attention due to differences regarding underlying genetic mutations. There is an ongoing debate if right- versus left-sided tumor location itself represents an independent prognostic factor. We aimed to investigate this question by using propensity score matching.
  
  
  
  Patients with resected, stage I - III colon cancer were identified from the Surveillance, Epidemiology, and End Results (SEER) database (2004-2012). Both univariable and multivariable Cox regression as well as propensity score matching were used.
  
  
  
  Overall, 91,416 patients (51,937 [56.8 %] with right-sided, 39,479 [43.2 %] with left-sided colon cancer; median follow-up 38 months) were eligible. In univariable analysis, patients with right-sided cancer had worse overall (hazard ratio [HR] = 1.32, 95 % CI:1.29-1.36, P < 0.001) and cancer-specific survival (HR = 1.26, 95 % CI:1.21-1.30, P < 0.001) compared to patients with left-sided cancer. After propensity score matching, the prognosis of right-sided carcinomas was better regarding overall (HR = 0.92, 95 % CI: 0.89 - 0.94, P < 0.001) and cancer-specific survival (HR = 0.90, 95 % CI:0.87 - 0.93, P < 0.001). In stage I and II, the prognosis of right-sided cancer was better for overall (HR = 0.89, 95 % CI:0.84-0.94 and HR = 0.85, 95 % CI:0.81-0.89) and cancer-specific survival (HR = 0.71, 95 % CI:0.64 - 0.79 and HR = 0.75, 95 % CI:0.70-0.80). Right- and left-sided colon cancer had a similar prognosis for stage III (overall: HR = 0.99, 95 % CI:0.95-1.03 and cancer-specific: HR = 1.04, 95 % CI:0.99-1.09).
  
  
  
  This population-based analysis on stage I - III colon cancer provides evidence that the prognosis of localized right-sided colon cancer is better compared to left-sided colon cancer. This questions the paradigm from previous research claiming a worse survival in right-sided colon cancer patients.
authors.affiliation: Department of Surgery, Kantonsspital St. Gallen, 9007, St. Gallen, Switzerland.|Institute of Medical Biometry and Informatics, University of Heidelberg, 69120, Heidelberg, Germany.
authors.forename: Rene
authors.initials: R
authors.lastname: Warschkow
authors.affiliation: Division of Gastroenterology and Hepatology, Kantonsspital St. Gallen, 9007, St. Gallen, Switzerland.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Sulz
authors.affiliation: Department of Surgery, Kantonsspital St. Gallen, 9007, St. Gallen, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Marti
authors.affiliation: Department of General, Abdominal and Transplant Surgery, University of Heidelberg, 69120, Heidelberg, Germany.
authors.forename: Ignazio
authors.initials: I
authors.lastname: Tarantino
authors.affiliation: Department of Surgery, Kantonsspital St. Gallen, 9007, St. Gallen, Switzerland.
authors.forename: Bruno M
authors.initials: BM
authors.lastname: Schmied
authors.affiliation: Division of Medical Oncology & Hematology, Kantonsspital St. Gallen, 9007, St. Gallen, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Cerny
authors.affiliation: Department of General, Abdominal and Transplant Surgery, University of Heidelberg, 69120, Heidelberg, Germany. ulrich.gueller@kssg.ch.|Division of Medical Oncology & Hematology, Kantonsspital St. Gallen, 9007, St. Gallen, Switzerland. ulrich.gueller@kssg.ch.|University Clinic for Visceral Surgery and Medicine, University Hospital Berne, 3010, Berne, Switzerland. ulrich.gueller@kssg.ch.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Güller
mesh_terms: D000230:Adenocarcinoma / Q000401:mortality* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000401:mortality* / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D057216:Propensity Score; D016016:Proportional Hazards Models; D018426:SEER Program
keywords: Colon cancer; Left-sided; Right-sided; SEER; Survival