Comparative epidemiology of cancers of the testis, lung, bladder and stomach with special reference to the possible implication of environmental hormones in the recent risk changes of the 4 neoplasia types.

Abstract

The purpose of this study is to extract common features of an environmental hormone-oriented neoplasia by comparatively investigating the epidemiological characteristics of testicular cancer in Denmark with those of other cancers, of which the age-adjusted incidence rates (AAIRs) underwent remarkable increase or decrease in the time range of early 1960's to mid 1980's. Practically, the log-transformed (log) AAIRs and the corresponding log ASIRs (age-specific incidence rates) were used in parallel to investigate the dynamic aspect of cancer risk changes in time and space. The present study includes cancers of the testis, lung, bladder and stomach as study subjects, and followed the chronological transition of cancer risk for each tumor type and for each population unit from early 1960's to mid 1980's. In space, the present study includes the data for 6 population units as follows: Denmark, Birmingham-England, the State of New York less New York city, Miyagi-Japan, Puerto Rico and Cali-Colombia. Since 3 neoplasias other than testicular cancer were associated with male predominance of cancer risk, 1st order regression analysis was applied to a set of 5 chronologically consecutive data of log AAIRs for a given tumor to comparatively investigate the sex discrimination of cancer risk for each of 3 neoplasia types. Results obtained are as follows: a) the ASIR profile of testicular cancer in Denmark (a high-risk country) was a composite of an adult type surge and an infant type surge (a product of in utero carcinogenic insult). Consistent ascension of both the adult type surge and the infant type surge of the ASIR profile was observed in parallel with the straight line increase of log AAIR of testicular cancer in Denmark. b) The ASIR profiles of testicular cancer for Miyagi-Japan (a low-risk country with steady increase of log AAIR) experienced new emergence of the infant type surge that was detectable in the profile for the years 1968-1971 and 1983-1987, but not in the profile for the years 1959-1960. c) The ASIR profiles of testicular cancer for Cali-Colombia (a low-risk country with no sign of risk increase) was free of the infant type surge throughout the study period. d) Temporary emergence of the infant type surge was experienced in cancers of the lung and bladder in early 1970's. In space, the infant type surge had preference of occurrence for a high-risk country to a low-risk country, and for a male population to a female population. e) Another feature of environmental hormone-oriented tumor was found in the recent risk decrease of gastric cancer of which the rate of risk decrease was distinct in Western countries and Japan, but not in Cali-Colombia. Puerto Rico was ranked as an in-between existence--a violation to the rules of Westernization effect for cancer risk. f) The relation between the male log AAIR and the male log AAIR less female log AAIR for a given tumor type was found to have a good fitness to the equilibrium model of which the members are destined to interact with each other under the law of mass action. The above mathematical strictness was found to be valid with all of cancers of the liver, skin, lung, bladder, stomach and esophagus--a finding to indicate that the relation between the changes of male cancer risk and that of female cancer risk in time and space is defined by the law of mass action regardless of the presence or absence of environmental hormone impact, and that no marker is available to detect possible implication of the environmental hormones with this system. g) The significance of the last finding in cancer etiology was discussed in the light of the steroid criminal hypothesis of human carcinogenesis in general. In conclusion, the recent risk changes of cancers of all the testis, lung, bladder and stomach in high-risk areas are in part to be explained in terms of the environmental hormone impact.