A birth cohort analysis of the incidence of ascending and descending colon cancer in the United States, 1973-2008.

Abstract

There is evidence indicating that the trends in colorectal cancer (CRC) incidence rates in the United States differ according to CRC subsites, including for ascending cancer which has shown a different pattern from the overall trends. We investigated the time trends for ascending and descending colon cancer in the United States by race and gender to identify the specific components that may account for the incidence trends. Using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program for 1973-2008, we conducted age-period-cohort modeling to evaluate birth cohort patterns and evaluate age-period-cohort effects on incidence trends of colon cancer over time. A clear birth cohort pattern was observed for both ascending and descending colon cancer, and the incidence rates of ascending colon cancer in the more recent birth cohorts were higher compared to earlier cohorts particularly for black males and females. This increase was most obvious in the younger age groups and appeared to accelerate, especially for black females. For descending colon cancer, the study suggested an increase in the birth cohort slope in the later birth cohorts for all gender and race groups, after a period of decline in earlier birth cohorts. The increase in incidence rates of both ascending and descending colon cancer in more recent birth cohorts for blacks suggests the need for targeted public health strategies to increase CRC screening. Further, additional etiological studies are warranted to evaluate factors responsible for the observed trends in more recent birth cohorts, including differences by subsites, race, and/or gender.