Background: Major medical organizations recommend periodic screening for colorectal cancer in some patients. Because colorectal cancer is more common in older patients, screening them may seem warranted; however, it is unclear whether these patients benefit from screening because many have one or more chronic illnesses and a short life expectancy. Most trials on colorectal cancer screening do not include patients older than 75 years. Studies have suggested that patients with a life expectancy of less than five years do not benefit from screening.

The Study: Gross and colleagues examined the relationship between age and life expectancy after a colorectal cancer diagnosis. The retrospective cohort study included data from the Surveillance, Epidemiology, and End Results Program–Medicare database (a population-based cancer registry). The study population included 35,755 patients 67 years or older who were diagnosed with colorectal cancer between 1993 and 1999.

Chronic conditions were identified by searching administrative patient claims from two years before to 60 days after cancer diagnosis. The most common conditions in this population were chronic obstructive pulmonary disease, heart failure, and diabetes. Patients were divided into three categories: no chronic conditions (40 percent), one or two chronic conditions (44 percent), or three or more chronic conditions (15 percent). Patients also were categorized into five-year age groups. This information was used to construct life-expectancy tables based on sex, age, chronic illness burden, and cancer stage.

Results: Overall, life expectancy after a colorectal cancer diagnosis diminished with increasing age, number of chronic conditions, and advanced cancer stage. The life expectancy of patients with stage I cancer was more strongly associated with chronic illness burden than with age. For example, an 81-year-old man with no chronic conditions would be expected to live more than 10 years, whereas a 76-year-old man with one or two chronic conditions or a 67-year-old man with at least three chronic conditions would be expected to live less than 10 years. Men and women 76 to 80 years of age with three or more chronic conditions would be expected to live five years or less. Patients with stage IV cancer had a uniformly poor prognosis, living on average less than one year after diagnosis.

Conclusion: The authors conclude that the presence of one or more chronic conditions is strongly associated with life expectancy after a colorectal cancer diagnosis. This association is strongest in patients with stage I cancers. The authors suggest that these findings may assist physicians in counseling older patients with multiple chronic conditions about the likelihood of benefiting from screening.