Trends in the death rates from cancers of the intestine (including colon and rectum) in Italy from 1956 to 1981 were analyzed with a standard cross-sectional approach and a log-linear age/period/cohort model. In both sexes there were steady increases in mortality rates between the middle 1950s and the middle 1970s, chiefly explainable in terms of cohort effects. This was followed by a leveling off and stabilization, starting from the younger age groups and more evident in women. The analyses of the geographic distribution of intestinal cancer mortality in the 95 Italian provinces during 1975 to 1977 showed higher rates in the north of the country and in large urban concentrations, and a bimodal distribution of mortality rates, whose minimum corresponded to a distinct north/south separation. Trend surface models fitted to intestinal cancer standardized mortality ratios showed a high determination coefficient even for the simplest models. Residuals, corresponding to outliers, were scattered in a few northern and central areas. In addition, mortality rates for cancers of the intestine in middle age people were considered according to geographic area of birth and residence at death. In both sexes rates of migrant populations were influenced both by area of birth and residence, and, in particular, there was a wide-spread unfavorable effect of residence on migrants from the South to the North (the major migrant flux in Italy). The temporal and geographic variations in intestinal cancer rates observed in this study indicate that Italy may well be a particularly interesting situation for etiologic investigations of colorectal cancers.
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