Introduction: Cancer survival is related not only to primary malignancy but also to concomitant nonmalignant diseases. The aim of this study was to investigate the prognostic capacity of four comorbidity indices [the Charlson comorbidity index (CCI), the Elixhauser method, the National Institute on Aging (NIA) and National Cancer Institute (NCI) comorbidity index, and the Adult Comorbidity Evaluation-27 (ACE-27)] for both cancer-related and all-cause mortality among colorectal cancer patients. A modified version of the CCI adapted for colorectal cancer patients was also built.
Methods: The study population comprised 468 cases of colorectal cancer diagnosed between 1 January 2000 and 31 December 2010 at a community hospital. Data were prospectively collected and abstracted from patients' clinical records. Kaplan-Meier method and multivariate logistic regression models were performed for survival and risk of death analysis.
Results: Only moderate or severe renal disease [hazard ratio (HR) 2.71, 95% confidence interval (CI) 1.11-6.63] and AIDS (HR 3.27, 95% CI 1.23-8.68) were independently associated with cancer-specific mortality, with a population attributable risk of 5.18 and 4.36%, respectively. For each index, the highest comorbidity burden was significantly associated with poorer overall survival (NIA/NCI: HR 2.14, 95% CI 1.14-4.01; Elixhauser: HR 1.98, 95% CI 1.09-1.42; ACE-27: HR 1.78, 95% CI 1.07-1.23; CCI: HR 1.68, 95% CI 1.05-1.42) and cancer-specific survival. The modified version of the CCI resulted in a higher predictive power compared with other indices studied (cancer-specific mortality HR = 2.37, 95% CI 1.37-4.08).
Conclusions: The comorbidity assessment tools provided better prognostic prevision of prospective outcome of colorectal cancer patients than single comorbid conditions.