Purpose:  In the U.S., nearly 70% of colorectal cancer (CRC) cases are diagnosed in individuals over age 65.  Absent screening and changes in risk factors, longer life spans may result in substantial increases in CRC cases as individuals are at risk for longer.  We examined the extent to which improvements in life expectancy in the U.S. affect CRC incidence and mortality. 

  Methods:  We developed a Markov model to predict lifetime risk of CRC incidence and mortality.  Age-specific probabilities of CRC diagnosis and cancer-specific mortality by stage were obtained from the Surveillance, Epidemiology, and End-Results Program.  Using CRC incidence and mortality from the pre-screening era in the late 1970s, we systematically varied U.S. all-cause mortality according to year- and race-specific life tables to isolate the effects of increased life expectancy.  Cohorts of 20-year-old men were analyzed as illustration.

  Results:  Life expectancy for 20-year-old U.S. white males increased from 49.8 years in 1960 to 55.3 years in 2000.  Holding all other factors constant at pre-screening levels, we predicted this increase in life expectancy over the 40-year period would result in a 44% increase in the lifetime risk of CRC incidence (from 4.5% to 6.5%) and a 50% increase in the lifetime risk of CRC mortality (from 2.5% to 3.7%).  In general, for each one-year increase in remaining life expectancy for white males, the lifetime risk of CRC incidence increased by 0.004.  In comparison to white males, life expectancy for black males was approximately 7 years less at both time periods.  Controlling for differences in underlying cancer incidence and mortality, the lower life expectancy experienced by black males was associated with a 25% reduction in lifetime risks of CRC incidence and mortality compared with white males.  In contrast, when we compared pre-screening incidence with the lower current incidence (year 2000) holding life expectancy constant at year 2000 we found approximately 13% reductions in lifetime CRC incidence and mortality.

  Conclusions:  The positive effects of increased screening and improved treatment over time on observed CRC incidence and mortality are counterbalanced by increases in life expectancy.  Because age-standardization of cancer statistics obfuscates the impact of increasing life expectancy, quantification of the relationship between life expectancy and colorectal cancer provides insights into the growing burden of disease.