Chronological transition of the age-adjusted incidence rates (AAIRs) of 20 major neoplasias from early 1960s to mid-1980s.

The purpose of this study was to investigate the chronological changes in the age-adjusted incidence rates (AAIRs) of cancers of all sites as well as of 20 major cancers worldwide, which were tested using 5 consecutive IARC Data books from the early 1960s to mid-1980s. We used log-transformed AAIR data (log AAIR) for the statistical analysis of group data. For the follow-up study of a given neoplasia, we prepared 5 world populations using 5 international Data books, and calculated the mean and standard deviation of log AAIR for each tumor, for each sex and for each of 5 world populations for the follow-up study of cancer risks of 20 major cancers as well as cancers of all sites. The results obtained are as follows: a) the log AAIR of cancers of all sites, as compared between the early 1960s group and the mid-1980s group, significantly increased in both the male population (+32.1%) and the female population (+18.0%). b) The remarkable decrease of risks (log AAIRs) for cancers of the stomach and the uterine cervix (non-Western type cancers) and a remarkable increase of risks for cancers of the lung of both sexes, and of the female breast (Western type cancers), were observed from the early 1960s to the mid-1980s--a finding to indicate that the Westernization influences the cancer risk world-wide. c) The follow-up study of cancer risks of individual tumors in both individual population units and the world populations revealed the presence of a number of cancer risk changes that do not fit the definition of "Westernization of cancer risk pattern": i) an abrupt and remarkable increase of skin cancer risk that took place in both the East and the West in the time range of early 1960s to early 1970s; ii) a remarkable increase of liver cancer risk in both the East and the West in the early 1960s to mid-1980s; iii) sex-discriminative cancer risk increase, as exemplified by the contrast between significant risk increase of male sex organs (the prostate and the testis) and complete lack of risk increase in the female sex organs (the uterus and the ovary). d) Evidence was presented to suggest the possibility that some environmental hormone(s) may be implicated in the above changes in cancer risk that do not fit the definition of the "Westernization of cancer risk pattern". e) The importance of interdisciplinary exploration was stressed when assessing the scope of environmental hazards for both the risk of cancers of all sites and the reproductive activity of the human being.