title: Case Mix Difference Can Affect Evaluation of Outcome of Treatment for Colorectal Cancer.
abstract: OBJECTIVE
  To explore the potential effects of patient selection, for example by organization, on survival as outcome parameter in colorectal cancer treatment.
  
  
  METHODS
  The main cohort was identified in a Hospital-based registry and outcome data of all 2,717 patients operated on for colorectal cancer between 2000-2011 were evaluated. A simulation of different center settings was performed using several potential selection criteria, including emergency cases, referral surgery and palliative resection, and used for comparison of outcome data.
  
  
  RESULTS
  Overall survival and cancer-specific survival can be significantly affected in both short-term (30-/90-day) mortality and long-term survival by factors of organizational level.
  
  
  CONCLUSIONS
  Survival data as an outcome parameter can be affected by the composition of the patient cohort and thus reflect possible selection bias for example due to organization, referral patterns and practice customs. This potential bias should be acknowledged when making inter-hospital comparisons of outcome.
authors.affiliation: Department of Surgery, Institute of Clinical Sciences, the Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden david.ljungman@vgregion.se.
authors.forename: David
authors.initials: D
authors.lastname: Ljungman
authors.affiliation: Department of Surgery, Institute of Clinical Sciences, the Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
authors.forename: Karl
authors.initials: K
authors.lastname: Kodeda
authors.affiliation: Department of Surgery, Institute of Clinical Sciences, the Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Derwinger
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000401:mortality*; D003953:Diagnosis-Related Groups; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D016896:Treatment Outcome; D055815:Young Adult
keywords: Selection; bias; hospital structure; outcome; survival