Descriptive epidemiology of colorectal cancer.

The purpose of this report is to present the descriptive epidemiology of colorectal cancer using the most recent data available to highlight two characteristics of the disease. First is the great variation which takes place in the frequency of this disease over geographic areas of all sizes. Colorectal cancer is common in most countries of North America and Europe, is rare in Asia and is particularly uncommon in Africa. Internationally, the variation in colon cancer is 60-fold, and within Europe there is a 4-fold difference in the incidence of colon cancer between areas with the highest and lowest rates. For cancer of the rectum, variation internationally is 18-fold and within Europe it is 3-fold. Within the United Kingdom, colon cancer is uniformly higher in the 5 Scottish Cancer Registry Regions than in their counterparts in England and Wales. Even within Scotland there is a 4-fold range of colon cancer incidence in rates, with the North and South clearly demarcated by a striking difference in colon cancer incidence in both sexes. Secondly, examination of international mortality rates for colorectal cancer demonstrates remarkable differences in trends over time between countries. In countries where colorectal cancer mortality rates were initially low, rates have increased substantially. In many countries where rates circa 1950 were moderately high, they have increased slightly or become stabilized. However, in countries such as Scotland, Canada, England and Wales and the United States, where rates were initially high, there have been gradual falls in mortality over time.