Multimorbidity and survival in older persons with colorectal cancer

OBJECTIVES: To ascertain the effect of common chronic conditions on mortality in older persons with colorectal cancer. DESIGN: Retrospective cohort study. SETTING: Population-based cancer registry. PARTICIPANTS: Patients in the Surveillance Epidemiology and End Results-Medicare linked database who were aged 67 and older and had a primary diagnosis of Stage 1 to 3 colorectal cancer during 1993 through 1999. MEASUREMENTS: Chronic conditions were identified using claims data, and vital status was determined from the Medicare enrollment files. After estimating the adjusted hazard ratios for mortality associated with each condition using a Cox model, the population attributable risk (PAR) was calculated for the full sample and by age subgroup. RESULTS: The study sample consisted of 29,733 patients, 88% of whom were white and 55% were female. Approximately 9% of deaths were attributable to congestive heart failure (CHF; PAR = 9.4%, 95% confidence interval (CI) = 8.4-10.5%), more than 5% were attributable to chronic obstructive pulmonary disease (COPD; PAR = 5.3%, 95% CI = 4.7-6.6%), and nearly 4% were attributable to diabetes mellitus (PAR = 3.9%, 95% CI = 3.1-4.8%). The PAR associated with CHF increased with age, from 6.3% (95% CI = 4.4-8.8%) in patients aged 67 to 70 to 14.5% (95% CI = 12.0-17.5%) in patients aged 81 to 85. Multiple conditions were common. More than half of the patients who had CHF also had diabetes mellitus or COPD. The PAR associated with CHF alone (4.29%, 95% CI = 3.68-4.94%) was similar to the PAR for CHF in combination with diabetes mellitus (3.08, 95% CI = 2.60-3.61%) or COPD (3.93, 95% CI = 3.41-4.54%). CONCLUSION: A substantial proportion of deaths in older persons with colorectal cancer can be attributed to CHF, diabetes mellitus, and COPD. Multimorbidity is common and exerts a substantial effect on colorectal cancer survival.