Incidence of colorectal adenocarcinoma by anatomic subsite

BACKGROUND: Colorectal adenocarcinoma may represent more than one disease process. Numerous epidemiologic studies suggest that rates of occurrence of colorectal adenocarcinoma at particular anatomic subsites (e.g., right colon, left colon, and rectum) may be associated with distinctive geographic, demographic, and risk factor profiles. This study explored time trends over a 22-year period of the incidence of adenocarcinoma of the colon and rectum at various subsites among patients of different race, gender, and stage of disease. METHODS: Data on the incidence of colorectal adenocarcinoma were obtained from a population-based cancer registry in the Detroit, Michigan area funded by the National Cancer Institute. Age-adjusted incidence rates were analyzed by year of diagnosis. Relative survival rates were also obtained for different race and gender categories, along with disease stage at diagnosis. RESULTS: A major rise was revealed in the incidence of adenocarcinoma in the right colon among African American men and women between the mid-1970s and the early 1980s. The rise was greatest among African American men and accounts for increases in late stage disease among them. Corresponding decreases in survival among African American men were noted. CONCLUSIONS: These findings indicated widely differing disease patterns based on anatomic subsite and patient demography and also indicated a need for targeted efforts at early detection of adenocarcinoma of the right colon among African Americans.