Cancers of the colon and rectum are the fourth most commonly diagnosed cancers and rank second among cancer deaths in the United States. The incidence rates show wide divergence by racial/ethnic group, with rates in the Alaska Native population that are over four times as high as rates in the American Indian population (New Mexico) for both men and women. There are only minor differences, between men and women, in the order of incidence rates by racial/ethnic group. After Alaska Natives, the next highest rates in men are among Japanese, black and non-Hispanic white populations. These are followed by Chinese, Hawaiians and white Hispanics; and then Filipinos, Koreans and Vietnamese. In women, Alaska Natives are followed by black, Japanese and white non- Hispanic Americans. Next are Chinese, Hawaiians, and Vietnamese; and finally white Hispanics, Koreans, and Filipinos. Incidence rates for both men and women are substantially lower among American Indians in New Mexico (18.6 per 100,000 in men, 15.3 per 100,000 in women).

In each racial/ethnic group, incidence rates for cancers of the colon and rectum among women are lower than those among men. Although the pattern of incidence rates by race/ethnicity is similar for each sex, the ratio of male-to-female rates varies. Among Filipinos and Japanese, men experience an excess of greater than 60%, while among American Indians, Alaska Natives and Vietnamese the male excess is much lower at only 13-22%. It is interesting that, although the Alaska Natives have the highest colorectal cancer incidence rates of all groups and the American Indians experience the lowest, the gender ratios of these two native American groups are similar.

Mortality patterns by race/ethnicity for cancers of the colon and rectum are similar to those for incidence, with several notable exceptions. Black, Alaska Native, and white non-Hispanic men and women, as well as Hawaiian and Japanese men, have comparatively high mortality rates. The high mortality rates among Alaska Natives and Japanese men are consistent with the high incidence rates in these groups. However, the mortality rates among white non-Hispanic and black men and women, and among Hawaiian men, appear disproportionately high.

Colon cancer accounts for 59% (Korean men) to 81% (Alaska Native men) of the combined colon and rectum cancer incidence rates. This is reflected in an racial/ethnic pattern for colon cancer incidence rates that is quite similar to the pattern for both sites combined. Incidence and mortality rates for cancers of the colon and rectum increase with age. Interestingly, the incidence rate for Hawaiian men is highest in the 55-69 year age group, and their mortality rate is second only to black men in this age group.

Migrant and other studies have provided very strong evidence that colorectal cancer risk is modifiable, and that differences in population rates may therefore be explained by lifestyle or environmental factors. Dietary factors and exercise appear to be very important. Migrants to the United States (from Japan and other countries where rates of colon and rectal cancer are lower than in the U.S.) have higher rates than do those who remain in their native country. Studies have shown that first and second generation American offspring from these migrant groups develop these cancers at rates reaching or exceeding those of the United States white population.

Source: Miller BA, Kolonel LN, Bernstein L, Young, Jr. JL, Swanson GM, West D, Key CR, Liff JM, Glover CS, Alexander GA, et al. (eds). Racial/Ethnic Patterns of Cancer in the United States 1988-1992, National Cancer Institute. NIH Pub. No. 96-4104. Bethesda, MD, 1996.

Graphs showing incidence and mortality for specific racial and ethnic groups including information that may not be discussed in the text above, is available at the NCI's Surveillance, Epidemiology, and End Results (SEER) Web site at: http://seer.cancer.gov/.

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