[Cancer epidemiology in Japan].

Cancer became the leading cause of death in Japan in 1981. In 1985, the cancer death rate was 156.1 per 100,000 population, and cancer deaths accounted for 25.0% of all deaths. The number of cancer deaths and the crude cancer death rate are still increasing in Japan, but the age-adjusted death rate from cancer has been stable in males and has been declining in females in recent years. Thus, the main reason behind the increase of cancer deaths in Japan is an increase in the aged population. In Japan, stomach cancer is the most common cancer in both males and females, but the stomach cancer death rate as well as the incidence rate have been declining in recent years. The death rates and incidence rates of cancers of the cervix, liver (female only), and esophagus (female only) have also been declining in recent years. The death rates and incidence rates for other cancers have been increasing in recent years. Among all increasing cancers, cancers of the lung, biliary tract, pancreas, ovary and prostate have shown a remarkable tendency to increase. Thus, the cancer pattern in Japan seems to be approaching, in general, that of Western countries. Although the reasons for these changes in the death rate and incidence rate of cancer by site are not clear, it is considered likely that changes in dietary habits, cigarette consumption, age of marriage, number of births and progress in cancer screening, diagnosis and treatment have contributed to those changes. Major risk factors for cancer were reviewed. Smoking and diet were considered the most important risk factors. The importance of primary prevention of cancer by life style modification was emphasized.