A case-control study of large bowel cancer in Japan.

This investigation of diet and other environmental factors reports on 588 patients with colorectal cancer and 1,176 hospitalized controls in three prefectures of Japan. Weak (not statistically significant) positive effects were found for social class and urbanization. The significant association of colorectal cancer with consumption of beef, string beans, or starches previously described for Hawaiian Japanese were not reproduced here. An association with hakusal (cabbage) agreed with other reports on a negative association with cruciferous vegetables. An analysis of the subset of cases in the low rectum yielded results similar to those for the total series. The failure to uncover important food effects in Japan is attributed to the difficulty of detecting case-control differences in areas with homogeneous diet practices. Further epidemiologic research aided by leads from ongoing work with animals may provide ideas for more sharply defined questions, should stress new approaches for more accurate diet histories, and should continue to emphasize tumor localization.