Background: In recent years, the mortality rate for colorectal carcinoma in Japan has rapidly been increasing, and there are indications that it may surpass that of gastric carcinoma, with colorectal carcinoma fast becoming one of the main targets of cancer treatment in Japan.
Methods: Eight thousand three hundred and eighty-six case records of colorectal carcinoma (4479 males and 3907 females; 4691 colon carcinoma cases and 3695 rectal carcinoma cases), diagnosed over 18 years from 1974 to 1991 in Aomori Prefecture, were analyzed.
Results: Age-adjusted incidence for colorectal carcinoma per 100,000 population were 12.6 and 8.7 for males and females, respectively, in 1974. The corresponding rates were 20 and 13.6, respectively, in 1980, and 42.5 and 25.6, respectively, in 1991. Among patients with colon carcinoma, a higher proportion have sigmoid colon carcinoma. The degree of increase in the incidence of sigmoid colon carcinoma was almost the same as that of right-sided colon carcinoma. By birth cohort analysis, among those born in 1934 or earlier, the incidence at the same age was higher in the younger population.
Conclusion: It is possible that the age-adjusted incidence of colorectal carcinoma in Japan will soon resemble that of the white population in the United States, in a manner similar to that of Japanese-Americans.