Between 1973 and 1991 the incidence rate of colon cancer increased 26.6% in blacks compared to 1.6% in whites. The mortality rate increased 12.4% in blacks but decreased 17.6% for whites. These observations have not been explained. In fact, black-white differences in colon cancer incidence and mortality have not been adequately studied. The investigators will conduct a population-based study of colon cancer in blacks and whites in a 33- county area of North Carolina. The primary goal of the research is to examine possible exposure, susceptibility and health care factors that might explain diverging incidence and mortality trends in blacks and whites.
The specific aims of this research are as follow. (1) To identify environmental and lifestyle risk factors for colon cancer in blacks and whites. This study will explore a range of exposures that may be related to colon cancer, with special emphasis on meat cooking practices and the heterocyclic amines generated during cooking. (2) To assess the prevalence of specific inherited susceptibility characteristics in a large mixed-race population. The study will focus on the known alleles of two human N-acetyltransferase enzymes (NAT2/NAT1) using DNA obtained from blood samples. (3) To assess the possibility of gene-environment interactions between exposures to dietary carcinogens and genetic susceptibility risk factors. (4) To explore whether the excess colon cancer mortality among blacks might be explained by differences in (a) exposure to environmental risk factors, (b) tumor characteristics, and/or (c) access or availability of health services. A secondary aim is to collect biological specimens for subsequent analyses such as the role of other inherited genetic characteristics and the presence or absence of specific somatic genetic alterations. The study will recruit 800 cases of colon cancer between the ages of 40-84 and 800 population-based controls. Cancer cases (400 blacks and 400 whites) will be identified using the rapid ascertainment system of the North Carolina Central Cancer Registry. Controls will be selected using the Department of Motor Vehicle Registry data for those under age 65 and HCFA files for those 65 and older. Dietary, lifestyle and environmental exposure information will be obtained for cases and controls by personal, in-home interviews. The interview instrument includes comprehensive questions concerning meat cooking practices, and it seeks information about education, occupational status, poverty, and health care access and utilization. DNA extracted from peripheral blood lymphocytes will be used to determine NAT genotypes.
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