Background: Descriptions of population characteristics for intestinal cancers frequently combine colon and rectal sites. However, some studies suggest that cancers of subsites in the intestinal tract may differ both by demographics and biology. Examination of colon and rectal cancers' characteristics separately could identify different risk profiles for these sites.
Methods: Data from combined National Program of Cancer Registries (NPCR) and Surveillance, Epidemiology, and End Results (SEER) databases were examined for risk characteristics by age, race, sex, and ethnicity, as well as for SEER-reported trends over 27 years.
Results: Males had higher incidences of both colon and rectal cancers, but this predominance was greater for rectal cancers. Colon cancer rates were higher for blacks than for whites but rectal cancer rates were slightly higher for whites than for blacks. The change in incidence rates by race occurred abruptly at sites in the lower colon. Asians had low rates of colon cancer, but their rectal cancer rates were similar to those of blacks. Trends for both sites showed declines in incidence rates in whites, but slight to no change in blacks. Mortality in blacks increased until about 10 years ago.
Conclusions: Colon and rectal cancer sites should be studied independently because of major differences in their characteristics. Age-specific incidence rates differ by race and site. Any effect from screening is difficult to demonstrate because of changes in procedures over time, resulting in different levels of effective detection in the intestinal tract, and because of slow acceptance of screening by the public.