title: Comparison of hazard of death following surgery for colon versus rectal cancer.
abstract: BACKGROUND
  Prognosis in cancer is usually assessed by use of Kaplan-Meier survival function estimate curves, which reflect survival, or the proportion of patients that will remain alive after a particular event at a given time. By contrast, hazard function represents the proportion expected to be deceased among those surviving at a given time after an event. Objectives To evaluate survival and hazard of death, in patients with colon cancer (CC) and rectal cancer (RC), as indices of prognosis.
  
  
  METHODS
  Colon and rectal cancer patients who underwent surgical resection with curative intent from 1996 to 2011 were studied. The hazard of death and survival patterns were assessed with Weibull Hazard models and Kaplan- Meier survival function estimate curves.
  
  
  RESULTS
  There were 119 CC and 250 RC patients included in the study. Median (Inter-quartile range: IQR) age of both groups was 58 (49 - 66.5) years. The median (IQR) followup time was 30 (12 - 72) months for CC and 30 (13 - 70) months for RC. Both groups were similar in comparison with regard to age (p=0.96), gender (p=0.56), tumour stage (p=0.33), vascular invasion (p=0.69), lymphatic invasion (p=0.33), perineural invasion (p=0.94), degree of tumour differentiation (p=0.38) and preoperative carcinoembryonic antigen levels (p=0.77). CC showed better overall survival compared to RC (p=0.03) with a 5-year survival rate of 72% versus 60% respectively. After curative resection, CC showed a 6% decrease in hazard of death with time compared with RC which showed a 1% increase in the hazard of death with time.
  
  
  CONCLUSIONS
  Among patients who underwent resectional surgery, CC had a better prognosis than RC.
authors.affiliation: CT Centre, Faculty of Medicine, University of Kelaniya, Sri Lanka. dileepa@kln.ac.lk.
authors.forename: D S
authors.initials: DS
authors.lastname: Ediriweera
authors.forename: S
authors.initials: S
authors.lastname: Kumarage
authors.forename: K I
authors.initials: KI
authors.lastname: Deen
mesh_terms: D000368:Aged; D003110:Colonic Neoplasms / Q000401:mortality* / Q000601:surgery; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012004:Rectal Neoplasms / Q000401:mortality* / Q000601:surgery; D015996:Survival Rate