The effect of age and chronic illness on life expectancy after a diagnosis of colorectal cancer: implications for screening

Background: Older adults with shorter life expectancies may receive less benefit from colorectal cancer screening than younger, healthier patients. Objective: To determine the degree to which life expectancy after diagnosis of an early-stage cancer varies according to age or coexisting chronic illness. Design: Retrospective cohort study. Setting: Population-based cancer registry with linked administrative claims data. Patients: Patients 67 years of age or older who received a diagnosis of colorectal cancer from 1993 through 1999. Measurements: Chronic conditions were identified by searching Medicare claims. Using a life-table approach, the authors quantified the degree to which life expectancy associated with each cancer stage at diagnosis varied with patient age, sex, and burden of chronic conditions. Results: The final study sample consisted of 35 755 patients. After accounting for cancer stage at diagnosis, the authors found that life expectancy was strongly related to both age and the burden of chronic illness. Among men who received a diagnosis of stage I cancer at 67 years of age, life expectancy decreased from 19.1 years (95% CI, 17.8 to 20.5 years) for patients with no chronic conditions to 12.4 years (CI, 11.4 to 13.5 years) for those with 1 or 2 conditions and 7.6 years (CI, 6.1 to 9.4 years) for those with 3 or more conditions. A similar trend was noted among female counterparts, with life expectancy decreasing from approximately 23 years to 16 years and 7 years for the 3 chronic condition groups, respectively. For men and women 81 years of age with no chronic illnesses, life expectancy after stage I cancer diagnosis was 10.3 years (CI, 9.2 to 11.9 years) and 13.8 years (CI, 12.3 to 15.3 years), respectively. Limitations: Administrative claims may not identify all chronic conditions. Life expectancy estimates at the population level are averages and, therefore, may not accurately predict the life expectancy of individual patients. Conclusions: Coexisting chronic illness is associated with a substantial reduction in life expectancy after diagnosis of early-stage colorectal cancer. Physicians should consider this when deciding whether to screen older persons.