Predictive validity of five comorbidity indices in prostate carcinoma patients treated with curative intent.
BACKGROUND
Comorbidity is important to consider in clinical research on curative prostate carcinoma because of the role of competing risks. Five chart-based comorbidity indices were assessed for their ability to predict survival.


METHODS
This was a case-cohort study of prostate carcinoma patient cohort treated with curative intent in Toronto and Southeast Cancer Care Ontario regions between 1990 and 1996; the subcohort was drawn from these men, whereas cases were cohort members who died from causes other than prostate carcinoma. Comorbidity data were obtained from medical charts (269 subjects). Vital status, age, area of residence, and socioeconomic status information were available. Predictive validity was quantified by the percent variance explained (PVE) over and above age using proportional hazards modeling.


RESULTS
The Chronic Disease Score (CDS) (PVE = 11.3%; 95% confidence interval [95% CI], 3.5-22.8%), Index of Coexistent Disease (ICED) (PVE = 9.0%; 95% CI, 2.9-17.9%), Cumulative Illness Rating Scale (CIRS) (PVE = 7.2%; 95% CI, 1.4-17.1%), Kaplan-Feinstein Index (PVE = 4.9%; 95% CI, 0.6-12.8%), and Charlson Index (PVE = 3.8%; 95% CI, 0.3-10.9%) each explained some outcome variability beyond age. PVE differences among indices were not statistically significant. A comorbidity identified at the time of cancer diagnosis was the cause of death in 59.2% of cases (75% for cardiac or vascular causes).


CONCLUSIONS
The better-performing, more comprehensive indices (CDS, ICED, and CIRS) would be useful in measuring and controlling for comorbidity in this setting. The CDS was easiest to apply and explained the most outcome variability.
Boulos
David L
DL
Division of Cancer Care and Epidemiology, Queen's Cancer Research Institute, Queen's University, Kingston, Ontario, Canada.
Groome
Patti A
PA
Brundage
Michael D
MD
Siemens
D Robert
DR
Mackillop
William J
WJ
Heaton
Jeremy P W
JP
Schulze
Karleen M
KM
Rohland
Susan L
SL
D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002423:Cause of Death; D015331:Cohort Studies; D015897:Comorbidity; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011471:Prostatic Neoplasms / Q000401:mortality / Q000628:therapy*; D012306:Risk; D016019:Survival Analysis; D016896:Treatment Outcome