Context Patients with cancer often have other medical ailments, referred to
as comorbidity. Comorbidity may impact treatment decision-making, prognosis,
and quality of care assessment.
Objective To assess whether comorbidity information can provide important prognostic
information in a hospital-based cancer registry.
Design, Setting, and Participants An observational prospective cohort study using comorbidity data collected
by trained hospital-based cancer registrars. Comorbidity was obtained through
medical record review using the Adult Comorbidity Evaluation 27, a validated
chart-based comorbidity instrument. A total of 17 712 patients receiving
care between January 1, 1995, and January 31, 2001, for the primary diagnosis
of new cancer of the prostate, lung (nonsmall cell), breast, digestive system,
gynecological, urinary system, or head and neck were included.
Main Outcome Measure Duration in months of overall survival.
Results A total of 19 268 patients were included in the study; median duration
of follow-up was 31 months. Of these patients, 1556 (8.0%) were excluded due
to missing or unknown data. Severity of comorbidity strongly influenced survival
in a dose-dependent fashion and the impact of comorbidity was independent
of cancer stage. Compared with patients without comorbidity, the adjusted
hazard ratio associated with mild comorbidity was 1.21 (95% confidence interval
[CI], 1.13-1.30), moderate comorbidity was 1.86 (95% CI, 1.73-2.00), and severe
comorbidity was 2.56 (95% CI, 2.35-2.81). Adjusted Kaplan-Meier survival curves
revealed that at any point in time the patients with more severe levels of
comorbidity had worse survival (partial χ23 due
to comorbidity, 523.54; P<.001). Model discrimination
ranged from 0.71 for head and neck to 0.86 for prostate cancers.
Conclusions Comorbidity is an important independent prognostic factor for patients
with cancer. The inclusion of comorbidity in hospital-based cancer registries
will increase the value and use of observational research.