SPATIAL-DISTRIBUTION OF ANATOMICAL SITES OF CANCER IN A QUEBEC CANCERREGISTRY

Knowledge of the spatial distribution of diseases provides useful info rmation in etiologic research and in implementation of preventive acti vities in community health. Spatial autocorrelation analysis is one of the Various methods that enables to determine spatial clustering of d iseases. This method has not been applied to lung, stomach and colon c ancer in Quebec. These cancers are frequent and are associated with en vironmental factors. The objectives of the study are to determine spat ial distribution of incidence rates of these cancer sites by sex and t o help generate etiologic hypotheses. Community health departments (CH Ds) of residence are considered as risk markers since their population and environment may be related to the selected cancer sites. Data wer e obtained from Quebec Cancer Registry. Rates were standardized by the direct method. Autocorrelation analysis was done through BW coefficie nt and Moran's coefficient I for correlograms. Results of standardized rates were compared to those of non standardized rates. Rates yielded the same results for the BW coefficient. Conversely, results were qui te different for the correlograms. This implies that results from stan dardized rates should be kept since the age structure of CHD populatio ns are different. Important variation in the level of spatial autocorr elation was found among the six sex-specific cancer sites. For male lu ng cancer and male stomach cancer first-order neighbouring CHDs showed similar incidence rates according to a geographic gradient. Female lu ng cancer exhibited spatial autocorrelation. Absence of spatial autoco rrelation for colon cancer suggests that CHD is not the appropriate sc ale for study of this cancer and allows use of conventional epidemiolo gic methods. These results are discussed in relation to current etiolo gic hypotheses. Lung and stomach cancers deserve further study.