Subsite-specific incidence rate and stage of disease in colorectal cancer by race, gender, and age group in the United States, 1992-1997

BACKGROUND. Subsite specific incidence rates of colorectal cancer vary cons iderably by age, gender, and race. This variation may be related not only t o distinctions in exposure to genetic and environment factors but also to c urrent strategies of early detection screening. Patterns of stage of diseas e in anatomic subsite may reflect the effect of screening. This study used the largest aggregation of cancer incidence data in the U.S. to examine sub site specific incidence rates of colorectal cancer and the relation of stag e of disease to anatomic subsites by race, gender, and age group. METHODS. Data on the incidence of invasive colorectal cancer were obtained from 28 population-based central cancer registries. Age-specific and age-ad justed rates and stage distributions were analyzed by subsite, race, and ge nder. RESULTS. The impact of screening can be observed in the percentage of local ized disease, which increased from 31.9% among cancers in the proximal colo n to 37.0% in the descending colon to 41.5% in the distal colorectum. Withi n the same subsite, blacks were less likely than whites to receive a diagno sis of localized disease and more likely to receive a diagnosis of distant disease whereas stage distributions were approximately the same for males a nd females. Blacks were more likely than whites to receive a diagnosis of p roximal colon cancer than distal colorectal cancer. The male-to-female rate ratios progressively increased from the proximal colon to the distal color ectum. The ratios of proximal-to-distal colorectal cancer gradually increas ed with advancing age. CONCLUSIONS. Differentials in stage of disease by subsites indicate a need for a targeted effort at early detection of cancer in the proximal colon. R isk factors and higher risk populations for colorectal cancers in each subs ite need to be studied further to guide actions for improving the efficacy of screening. (C) 2001 American Cancer Society.