Epidemiology of breast cancer in Japan

Breast Cancer Vol. 2 No. 1 April 1995

Review Article

Epidemiology of Breast Cancer in Japan S U K E T A M I T O M I N A G A .1 A N D T E T S U O K U R O I S H 1 . 2

The mortality and incidence of breast cancer are high in Western industrialized countries and relatively low in developing countries in Asia and other parts of the world. In Japan the mortality of breast cancer has gradually been increasing, but is still much lower compared with those of Western countries. Within Japan the mortality of breast cancer is higher in urban areas than in non-urban areas. The future estimation of cancer incidence in Japan predicts that breast cancer will become a leading cancer in the near future. From the present review of epidemiology of breast cancer it is recommended that excess intake of fat and calories, especially of animal fat, be avoided.

Breast Cancer 2:1-7, 1995

Key words: Breast cancer, Epidemiology, Mortality, Incidence, Japan

International Comparison o f the Breast Can- cer Morta l i t y

Breast cancer is one of the major cancers in females. The mortali ty and incidence of breast cancer are high in Western industrialized countries and relatively low in developing countries in Asia and other parts of the world. Figure 1 shows the age-adjusted mortali ty rates of 34 countries/ races in 1983-19871). The mortal i ty of breast cancer is high in England and Wales, Scotland, and some other northern European countries, whereas the mortal i ty is low in Japan, Mexico, Hong Kong and some other countries in Asia and central and south America. Figure 2 shows the time trends of the age-adjusted mortali ty of breast cancer from 1953-1957 to 1983-1987 for selected countries in the world 1). The mortal i ty of breast cancer has stabilized in countries where the mortali ty was high and has been increasing in countries where the mortali ty was low. A marked increasing trend of breast cancer mortali ty can be observed in Czechoslovakia and Spain. The mortali ty in Japan has gradually been increasing, but is still low.

*2Division of Epidemiology, *iAichi Cancer Center Research Insti- tute. Reprint requests to Suketami Tominaga, Aichi Cancer Center Research Institute, 1-1, Kanokoden, Chikusa-ku, Nagoya 464, Japan.

Received October 5, 1994

Fig i. Age-adjusted death rates* of breast cancer in 34 countries/races (1983-1987). *Standardized based on the World population. From Kuroishi et aP ).

Trends in the Breast Cancer Morta l i t y and Rela ted Factors in Jaapn

Figure 3 shows the trends of the number of deaths from breast cancer, the crude and age- adjusted death rates of breast cancer from 1960 to 19902) . The number of deaths and the crude

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Tominaga S & Kuroishi T Epidemiology of Breast Cancer in Japan

death rate of breast cancer have increased markedly in the past 30 years, whereas the age-adjusted mortali ty of breast cancer has increased only moderately. Figure 4 shows the age-specific death rates for 1960, 1970, 1980 and 1990. An increasing trend is more markedly observed for the age groups of 50 to 70 years old.

To study the possible reasons for the increasing trend of breast cancer mortal i ty in Japan, trends of several factors possibly related to the cause of breast cancer were examined. Figure 5 shows the trends in the birth order for babies born in each year and the average age of mothers at birth of the first child a). Results in Fig 5 clearly

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Fig 4. Trends in the age specific death rate of breast cancer in Japan (1960-1990). From Kuroishi et al 2~.

Fig 5. Trends in the birth order and the average age of mother at the first child in Japan (1950- 1990). From Vital statistics of Japan 3).

Fig 6. Relative changes in food/nutrient intake in Japan (1955-1990). From National Nutrition Survey.

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Tominaga $ & Kuroishi T Epidemiology of Breast Cancer in Japan

Fig 8. Age-adjusted death rates of breast cancer in five areas with different population size in Japan (1981 1983). From Kato et al 4~.

Fig 9. Comparison of intakes of some selected food/nutrients in five areas with different population size in Japan (1966-1968, 1978 1980). From Kato et al 4~.


show that the number of children has been decreasing and the average age of the mother at the birth of the first child has been increasing; both of which are compatible with an increase of breast cancer. Among environmental risk factors, diet, especially high fat /calor ie intake is regarded as an important risk factor of breast cancer. Figure 6 shows the relative trends in selected food and nutrient intake in Japan. A marked increasing trend is observed for meat, milk and fat intakes, whereas the caloric intake has been stable over the last 35 years. Thus, it is likely that fat intake, especially of animal origin, has contributed much more to the increase of breast cancer in Japan than caloric intake. Kato et al further examined the chronological relations between the intake of selected food and nutrients and the breast cancer mortal i ty con- sidering some time-lag between the intake of food/nutrient and the death from breast cancer 4). They confirmed quantitatively the close positive correlation between the intake of fat, dairy products, butter and margarine, oils and fats, meat, cheese and some other animal foods and the breast cancer death rate.

number of children, etc may be related to urbanization.

Recent Results of Migrant Study of Breast Cancer

From many migrant studies 6-11) the influence of some environmental factors has been implicated. Figure 10 shows the age adjusted incidence rates of breast cancer for selected countries and races. The original data were abstracted from the Cancer Incidence in Five Continents, Volume VI TM Japanese, Chinese and Indians living in home countries and other Asian countries show a low rate of breast cancer, whereas Japanese and Chinese living in the United States show a much higher incidence rate, close to those of whites in the United States. These results confirm the influence of some environmental factors, possibly diet, especially high fat intake, on the incidence of breast cancer.

Future Prediction of Breast Cancer in Japan Tsukuma et al has predicted the future inci-

dence of selected sites of cancer in Japan up to

Geographical Distribution of Breast Cancer and Related Factors in Japan

Figure 7 shows the map of the age-adjusted death rate of breast cancer in the five years of 1988-1992 by prefecture in Japan s) . The mortali ty is high in Tokyo and other prefectures where metropolitan cities are located. Kato et al

compared the age-adjusted death rates of breast cancer in five areas with different population sizes in 1981-1983 in Japan and observed a close relation between urbanization and breast cancer mortali ty (Fig 8) 4) . To study the possible risk factors behind the urbanization, they compared the intake of selected food and nutrients for the five areas and found that the intake of butter and margarine, meat and fat was higher in urban areas than in non-urban areas (Fig 9) 4). Kato et

al further examined the correlation between the food/nutrient intake and breast cancer death rate among 12 geographical districts in Japan and confirmed the close positive relations between the intake of butter and margarine, cheese, ham and sausage, bread, dairy products, animal pro- tein and fat and the breast cancer mortali ty 4). Some other factors such as age at marriage, age of mother at the delivery of first child and the

Fig 10. Comparison of the incidence rates of breast cancer for selected races and countries in the World. Standard- ized based on the World population. From Cancer Inci- dence in Five Continents, Vol.VI TM.

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Tominaga S & Kuroishi T Epidemiology of Breast Cancer in Japan

Fig 11. Prediction of the age-adjusted incidence rates* of cancers for selected sites up to the year 2015 in Japan (females). *Standardized based on the World population. Tsukuma et al TM.

Fig 12. Prediction of the number of cancer incidences for selected sites up the year 2015 in Japan (females). From Tsukuma et al TM.

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Breast Cancer Vol. 2 No. 1 Ap~Jl 1995

the yea r 2015 by ex t r apo la t i ng the past t rends of sex and age-speci f ic incidence for selected sites TM. According to their predict ion, the age- adjusted incidence ra te of b reas t cancer will exceed tha t of s tomach cancer in the immedia te future; a round 1995 (Fig 11) and the incidence of

b reas t cancer will also exceed tha t of s tomach cancer by 2015 (Fig 12). Thus, b reas t cancer will become a majo r cancer among females in J apan

in the future.

Prevent ion o f Breas t Cancer As breas t cancer has been increas ing in J apan

and is predic ted to increase fur ther in the future, effect ive prevent ive measures , especia l ly p r im a ry preven t ion of b reas t cancer, should be taken. F o r p r ima ry preven t ion of b reas t cancer it is p roposed to avoid high r isk factors , especial ly avoidable risk fac tors such as excess fa t and calor ie intake. It is also desi rable f r om the v iew point of epidemiology and preven t ion to avoid a high mate rna l age at the del ivery of the first child, but this may not necessar i ly be easy f rom a soc ioeconomica l view point. T o compensa te for the difficulties in p r ima ry p reven t ion of b reas t cancer, secondary preven t ion of b reas t cancer; b reas t cancer screening by b reas t self examina- tion, physical examina t ion by phys ic ians and by m a m m o g r a p h y should be promoted .

References

1) Kuroishi T, Hayakawa N, Kurihara M, et al: Age- adjusted death rates from malignant neoplasms by site in 33 countries of the World (1953-1957 to 1983- 1987). In: Tominaga S, Aoki K, Fujimoto I, Kurihara Meds, Gann Monograph on Cancer Research No.41; Cancer Mortality and Morbidity Statistics Japan and World- 1994, Japan Scientific Societies Press, Tokyo, pp167-230, 1994.

2) Kuroishi T, Hirose K, Tajima K, et al: Cancer mortal-

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3) Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare: Vital Statistics of Japan, 1992, Vol.1, Kosei-tokei-kyoukai, Tokyo, pp99-103, 1994.

4) Kato I, Tominaga S, Kuroishi T: Relationship between westernization of dietary habits and mortality from breast and ovarian cancers in Japan. Jpn J Cancer Res (Gann) 78:349-357, 1987.

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7) Buell P, Dunn JF Jr: Cancer mortality among Japanese Issei and Nisei of California. Cancer 18:656 -664, 1965.

8) Haenszel W, Kurihara M: Studies of Japanese migrants, 1; Mortality from cancer and other diseases among Japanese in the United States. J NatI Cancer Inst 40:43-68, 1968.

9) Tominaga S: Cancer incidence in Japanese in Japan, Hawaii, and Western United States. Natl Cancer Inst Monogr 69:83-92, 1985.

10) Shimizu H, Mack TM, Ross RK, et al: Cancer of the gastrointestinal tract among Japanese and white immigrants in Los Angeles County. J Natl Cancer Inst 78:223-228, 1987.

11) Thomas DB, Karagas MR: Cancer in first and second generation Americans. Cancer Res 47:5771-5776, 1987.

12) Cancer Incidence in Five Continents, Volume Vi, IARC Scientific Publication No.120, Parkin DM, Muir CS, Whelan SL, Gao YT, Ferlay J, Powell J eds, International Agency for Research on Cancer, Lyon, pp956-957, 1992.

13) Tsukuma H, Kitagawa T, Hanai A, et al: Future prediction in cancer incidence in Japan. In: Tominaga S, Aoki K, Hanai A, Kurihara M eds, Gann Tokei Hakusho; Rikan/Sibou/Yogo-1993 (Cancer Statistics White Paper; Incidence/Mortality/Survival-1993), Shinohara Shuppan, Tokyo, pp153-170, 1993.

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Epidemiology of breast cancer in Japan