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1A.L. Ronco and E. De Stéfani, Nutritional Epidemiology of Breast Cancer, DOI 10.1007/978-94-007-2397-9_1, © Springer Science+Business Media B.V. 2012

Breast cancer (BC) in women is a major health burden worldwide. It is the most frequent cause of cancer among women in both developed and undeveloped societ-ies (Fig. 1.1 ), and is responsible for more than one million of the estimated 10 million of cancers diagnosed worldwide each year in both sexes [ 1 ] . It is also the primary cause of cancer death among women globally, responsible for 23% of the total new cancer cases and 14% (458.400) of the total cancer deaths in 2008 [ 2 ] .

Figure 1.2 shows the geographical variation in BC incidence worldwide, as esti-mated for the year 2008. The highest incidence rates occur in Northern and Western Europe, North America, Australia and New Zealand, Israel and in Southern Latin American are two exceptions: Uruguay and Argentina. According to GLOBOCAN [ 2 ] , the incidence age-adjusted rate in the more developed areas is currently 66.4/100.000 women compared to 27.3/100.000 in the less developed areas. Also mortality is higher in the developed societies, when it is compared to the one in the less developed countries: 15.3/100.000 vs. 10.8/100.000 respectively. Cancer survival tends to be poorer in developing countries, most likely because of a combination of a late stage at diagnosis and limited access to timely and standard treatment [ 3 ] .

Although BC is still a major public health issue in developed societies, its inci-dence has been rising in several developing countries over the past few years. International data [ 1 ] indicate that Uruguay is among those with the highest rates in the world. Furthermore, its capital city, Montevideo, displays the highest incidence rate for a city until new data are published. Albeit Uruguay is a South American developing country, it shares some features of developed societies, i.e. a very high level of red meat consumption [ 4 ] , a high human development index (50º in the world ranking according to United Nations, by factors as birth rate, infant mortality, life expectancy, literacy among others) [ 5 ] and an aged population [ 6 ] . In other words, a developing country has displayed a high occurrence of a disease typical of developed countries. The fact that the above quoted countries are cattle producers and high meat consumers might not be a coincidence: Uruguay is the country with the highest beef per capita intake in the world [ 7 ] .

Being a developed country is not mandatory for having high incidence rates: Japan, for example, has lower rates than the quoted countries from Northern hemisphere.

Chapter 1 General Epidemiology of Breast Cancer

2 1 General Epidemiology of Breast Cancer

Conversely, countries as Uruguay and Argentina have shown higher rates in the region than in the rest of the Latin American developing countries.

As a result of the ‘westernisation’ of lifestyles (change of habits, stronger urban-ization, increase of educational levels) the occurrence of BC increases. The inci-dence ranking of the last years has notably changed, due to the rise. The most rapid rises have been seen in developing countries, including some of them which belonged to the former Soviet Union and some other underdeveloped ones, where BC risk has historically been low relative to industrialised societies [ 8 ] . Urbanization implies an

Breast

Cervix uteri

Colorectun

Lung

Stomach

Corpus uteri

Ovary

Liver

Thyroid

Leukaemia

Non-Hodgkin lymphoma

Oesophagus

Pancreas

Brain, nervous system

Kidney

0 10 20 30 40ASR (W) rate per 100,000

IncidenceMortality

Fig. 1.1 Bar graphics showing the incidence of female cancers in the world


increase in job types that are less active than rural ones: outdoor jobs performed by women, regardless of their conditions, are associated with high caloric- and fast-foods and this is favourable for the development of health problems such as excess weight and obesity. Also psychosocial stress might play a role [ 9 ] , albeit it can be diffi cult to quantify. Higher educational levels correspond to a reduction in the average number of pregnancies and births, an increase of age at the fi rst birth, as well as reduced times of breastfeeding.

Therefore, as a consequence of changing exposures to reproductive and nutrition-related determinants over time, it should be recognized that women are at increas-ingly high risk of BC in most regions of the world during the past few decades [ 8 ] . The most severely affected women from developing countries, at least within the Latin America region, are those who belong to the mid-to-high socioeconomic and cultural classes and who accumulate menstrual and reproductive risk factors with some environmental ones. Due to such socio-economic and environmental factors, we have recognized that these women belong to a “fi rst world” within the third world [ 10 ] , in other words, women have been acquiring a profi le which is closer to that of women in industrialized countries. Additionally, an increased screening intensity can explain partially the quoted rise in incidence [ 11 ] .

0 18.9 27.2 40.1 67.5 110Age-standardised incidence rates per 100,000

Roll over the map for country rates.Click onto the map and zoom with mouse wheels

GLOBOCAN 2008, International Agency for Research on Cancer

Breast Cancer Incidence Worldwide in 2008

Fig. 1.2 Breast cancer incidence worldwide: age-standardised rates (world population) (Source: Ref. [ 2 ] )


Risk Factors

Estrogens were recognized fi ve decades ago as the main risk factor for developing BC [ 12 ] . Currently, the importance of other risk factors different from the classic ones (menstrual and reproductive factors and family history of cancer) has been somehow underestimated until few years ago, in our opinion. In general, the high rates of BC in developed societies are a consequence of a higher prevalence of the known “classic” risk factors for the disease, many of which – early age at menarche, nulliparity, late age at fi rst birth, late age at any birth, low parity, and late menopause – relate to the hormonal (specially estrogen) milieu to which the breast is exposed from menarche to the cessation of ovulation at menopause [ 13 ] .

Previous knowledge on classic risk factors (menstrual-reproductive history and family history) has led to the idea that women who have been exposed for a longer time period or more intensely to endogenous estrogens will have an increased risk of BC. However, scientifi c research has demonstrated that diet, fat excess and a low level of physical activity can also strongly affect the hormonal production and avail-ability, independently from having or not any of the quoted “classic” risk factors [ 14, 15 ] . The higher parity and earlier age at fi rst pregnancy of women seen in many developing countries might account for part of the lower incidence of BC in these regions relative to developed countries. The greater risk for women from affl uent (developed) backgrounds is, however, outweighed by their lower mortality. On the other hand, women from deprived backgrounds often present more advanced stages of the disease, and this applies not only to BC but cancers in general [ 3 ] .

Exposure to exogenous hormones as oral contraceptives [ 16 ] and hormone replacement therapy [ 17 ] result in an increase in the risk of BC. Incidence rates in some of the developed countries, including the United States, United Kingdom, France, and Australia, sharply decreased from the beginning of the current century, in part due to a lower use of combined postmenopausal hormone therapy [ 18– 22 ] . On the contrary, BC mortality rates have been decreasing in North America and several European countries over the past 25 years, largely as a result of early detec-tion through mammography and improved treatment [ 11, 23, 24 ] .

Excessive alcohol intake also seems to increase risk, with a recent re-analysis of 53 studies indicating that about 4% of BCs in developed countries might be attribut-able to its consumption [ 25 ] . The accompanying evidence on exposure to endoge-nous and exogenous oestrogen indicates that the lifetime length of exposure to endogenous oestrogen has been increasing, which is consistent with upward trends in incidence of BC, particularly in developed countries.

The changing patterns of childbearing and breastfeeding, of exogenous hormonal intake and of dietary factors including obesity and reduced physical activity have certainly contributed to trends in incidence and mortality. Currently, the experts suggest that maintaining a healthy body weight, increasing physical activity, and minimizing alcohol intake are the best available strategies to reduce the risk of developing BC [ 26 ] . Early detection through mammography has been shown to increase treatment options and at the same time to save lives, although this approach

5References

is not feasible in most economically developing countries due to its costs [ 27 ] . Recommended early detection strategies in these countries include the promotion of awareness of early signs and symptoms and screening by clinical breast examina-tion [ 28 ] . The recognition that several particular factors have contributed to the incidence of BC in different populations worldwide has meant a major challenge. The underlying reasons are multiple and interactive. The analysis of the possible role of nutrition as an indicator of the major factor, lifestyle, and its relationships with BC is the main purpose of this book, since this information has potential impact on public health.

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