Possible implication of environmental hormones in the recent risk increase of cancers of the skin and the liver, but not of the female breast worldwide.
The invention of 2 contrasting terms "Western type cancer" and "non-Western type cancer" implies that the progress of Westernization of life style for a given population may find its reflection in the balance of cancer risk between a Western type cancer and a non-Western type cancer. Our recent investigation presented evidence to indicate that the incidence of cancers of all sites increased by 32.1% (males) and 18.0% (females) from early 1960s to mid 1980s in the world statistics, and that the observed risk increase of cancers of the skin and liver did not fit the definition of "Westernization effect". It was suggested that the spread of environmental hormones could be related to the increased risks of 2 cancers. This study attempted to test the validity of the above statement by studying comparatively the epidemiological aspects of cancer of the skin, liver and breast, the latter being the reference tumor of the "Westernization effect". Cancer risk for each tumor was expressed in terms of the age-specific incidence rate (ASIR) and age-adjusted incidence rate (AAIR). For mathematical reasons, both ASIR- and AAIR-data were transformed into their logarithms before statistical analysis. We prepared the world population model with a size of 38 population units to investigate the relation between reproductive activity and cancer risk. Results obtained are as follows: a) the log AAIR of liver cancer was positively correlated to 2 parameters of reproductive activity in the female world population, and failed to show any correlation to the same 2 parameters in the male world population. The above finding was taken as evidence to indicate that liver cancer still retained its characteristics as a cancer of non-Western type with male predominancy of cancer risk. b) The log AAIR of skin cancer was negatively correlated to 2 parameters of reproductive activity in the world populations of both sexes--reconfirmation of skin cancer as of the Western type. c) In the period of early 1960s to mid 1980s the log AAIR of liver cancer of both sexes underwent exponential growth in Japan, slow and straight-line growth in 3 non-hispanic White populations, and no significant change in 2 Hispanic populations. d) The chronological follow-up study of log ASIR profile of both liver cancer in Japan and skin cancer in England revealed 3 common traits of cancer risk boost: i) quick and distinct ascension of cancer risk of all ages; ii) elongation of the young- age tail of the ASIR profile towards the 0 year limit; iii) emergence of a new infant type cancer profile independent of the existing adult type cancer profile. Possible implication of environmental hormones in human embryogenesis was suggested as an explanation for the genesis of an infant type cancer. e) Comparative study of log ASIR profiles of breast cancer between England and Japan did not support possible implication of environmental hormones in the recent rise of breast cancer risk throughout the world. f) The eligibility of cancers of the liver and skin as the targets of environmental hormones was discussed in the light of up-to-date data of epidemiology and experimental pathology.
Kodama
M
M
Kodama Research Institute of Preventive Medicine, Nagoya, Japan.
Murakami
M
M
Kodama
T
T
D000367:Age Factors; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology; D002274:Carcinogens, Environmental / Q000009:adverse effects*; D005006:Ethnicity; D005260:Female; D006728:Hormones / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008113:Liver Neoplasms / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D011158:Population Growth; D012044:Regression Analysis; D018570:Risk Assessment; D012737:Sex Factors; D012878:Skin Neoplasms / Q000453:epidemiology* / Q000209:etiology; D013995:Time
D002274:Carcinogens, Environmental; D006728:Hormones