Approximately 149,000 new cases of colorectal cancer were projected for 1994, representing nearly 15 percent of all cancers diagnosed that year in this country. Colorectal cancer ranks second in cancer incidence for the combined U.S. population. The incidence of colorectal cancer, as with many malignancies, is extremely low in childhood, increasing dramatically with age. The median age at diagnosis of colorectal cancer in the United States is 70 for men and 73 for women. Incidence rates among blacks have caught up with those in whites over the last 15 years.
Mortality rates are slightly higher in blacks than whites for both men and women.
In general, colorectal cancer rates, unlike those for cancers of the lung, cervix, and prostate, for example, show little socioeconomic gradient in the United States and other developed countries. A rapid rise in colorectal cancer rates in a particular area signals the action of environmental factors. Especially noteworthy in these Australian findings is the relatively rapid convergence in colorectal cancer rates within the life span of the migrants. In line with the evidence cited above, dietary intake varies considerably across countries, has changed over time in countries like Japan, and may be altered substantially during acculturation following migration. Epidemiologic studies have generally shown a direct association between fat intake and colorectal cancer risk.