Cancer incidence in Japanese in Japan, Hawaii, and western United States.

We based our systematic review of the cancer incidence rates of 48 anatomic sites of Japanese in Japan (Miyagi, Osaka, and Fukuoka Prefectures) and Japanese and Caucasians in the United States (Hawaii, San Francisco Bay Area, and Los Angeles County) on the cancer incidence data included in volume IV of "Cancer Incidence in Five Continents." Cancer sites were classified into 10 categories according to the trend of cancer incidence among the 3 groups. To evaluate the influences of environmental and racial factors, we used the ratio of cancer incidence in Japanese living in the United States to that of native Japanese, and the ratio of cancer incidence in Caucasians to that of Japanese living in the same areas of the United States. The present study revealed that the risks of cancers of the prostate, corpus uteri, colon, thyroid, breast, ovary, and testis were elevated, whereas those of the stomach, esophagus, and cervix uteri were decreased in the United States. Caucasians were more susceptible to melanoma, cancers of the mouth, lip and vermilion border, tongue, oropharynx, and larynx than were the Japanese, but the Japanese were more susceptible to cancers of the stomach, gallbladder, and liver. The difficulties we encountered in differentiating the influences of environmental factors from those of genetic racial factors are discussed. The necessity for further observations of the life-style (especially dietary habits) and the cancer incidence of Japanese living in the United States and comparisons with those of native Japanese and Caucasians are emphasized.