title: Measuring comorbidity in patients with head and neck cancer.
abstract: BACKGROUND
  Comorbidities are diseases or conditions that coexist with a disease of interest. The importance of comorbidities is that they can alter treatment decisions, change resource utilization, and confound the results of survival analysis.
  
  
  OBJECTIVE
  The objective of this study was to determine the best comorbidity index to use in survival analysis of patients with squamous cell carcinoma of the head and neck.
  
  
  METHODS
  Four validated indexes, with very different methodologies (i.e., the Charlson Index, the Cumulative Illness Rating Scale, the Kaplan-Feinstein Classification, the Index of Co-existent Disease), were tested using data from 379 unselected consecutive patients with complete 3-year follow-up from the Kingston Regional Cancer Center. Kaplan-Meier analysis and Cox Proportional Hazards Regression were used to stratify patients into three levels of increasing severity of comorbidity for each index. The Proportion of Variance Explained and Receiver Operating Characteristics curves were used to compare the performance of the indexes.
  
  
  CONCLUSIONS
  The Kaplan-Feinstein Classification was the most successful in stratifying patients in this population.
authors.affiliation: Department of Otolaryngology, Queen's University, Kingston, Ontario, Canada. sfh@post.queensu.ca
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Hall
authors.forename: Paula A
authors.initials: PA
authors.lastname: Rochon
authors.forename: David L
authors.initials: DL
authors.lastname: Streiner
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Paszat
authors.forename: Patti A
authors.initials: PA
authors.lastname: Groome
authors.forename: Susan L
authors.initials: SL
authors.lastname: Rohland
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology*; D015897:Comorbidity; D005260:Female; D006258:Head and Neck Neoplasms / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D016016:Proportional Hazards Models; D012372:ROC Curve; D012189:Retrospective Studies; D016019:Survival Analysis