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Global trends in breast cancer

Press release issued: 20 April 2005

Global trends in breast cancer incidence and mortality are the subject of new research published today in the International Journal of Epidemiology (IJE), edited in the Department of Social Medicine at Bristol University.

Global trends in breast cancer incidence and mortality are the subject of new research published today in the International Journal of Epidemiology (IJE), edited in the Department of Social Medicine at Bristol University.

Dr Michelle Althuis and colleagues at the National Cancer Institute, Rockville, USA analysed incidence and mortality rates for breast cancer over three decades (from 1973 to 1997) and across several continents.  

Breast cancer is the most common cancer among women worldwide and it exceeds lung cancer as the leading cause of cancer deaths among women.  In 2000 alone, more than one million women were diagnosed (22 per cent of all female cancer diagnoses) and 373,000 women died (14 per cent of all cancer deaths among women).

The study found that both breast cancer incidence and mortality rates varied four-fold by geographic location between countries with the highest and lowest rates.  Recent (1993-1997) incidence rates ranged from 27 per 100,000 in Asian countries to 97 per100,000 among US white women.

Overall, North American and northern European countries had the highest incidence rates of breast cancer; intermediate levels were reported in Western Europe, Oceania, Scandinavia, and Israel; and the lowest levels were in Eastern Europe, South and Latin America, and Asia.

 Breast cancer incidence rose 30-40 per cent from the 1970s to the 1990s in most countries, with the most marked increases among women aged fifty years and older.

Mortality from breast cancer paralleled incidence: it was highest in the countries with the highest incidence rates (between 17 per 100,000 and 27 per 100,000), lowest in Latin American and Asia (7-14 per 100,000), and rose most rapidly in countries with the lowest rates.  

Breast cancer incidence and mortality rates remain highest in developed countries compared with developing countries, as a result of both the use of different screening mammograms and disparities in lifestyle and hereditary factors.

Dr Althuis said: “Although race and ethnicity are strong predictors of breast cancer, studies assessing determinants of risk for women who migrate from areas of low to high incidence suggest that international differences are social and environmental in addition to hereditary in origin.

“Much of the variability in global breast cancer rates has been attributed to country-specific differences in the prevalence of risk factors that determine lifetime exposure to oestrogen, for example, comparatively younger ages at menarche, older ages at first birth and/or menopause, and higher prevalence of post-menopausal obesity.  Cross-cultural differences in height, diet, alcohol consumption and exogenous oestrogen use are also believed to contribute to international differences.

“Between 1973 and 1997 breast cancer incidence increased worldwide, although patterns of increase varied with geographic location.  In North America, incidence rates rose through the 1980s, but the increases have slowed in the mid-1990s.  Rates throughout the rest of the world generally increased most dramatically after the mid-1980s and continued to rise. 

“Although breast cancer incidence is on the rise worldwide, breast cancer mortality has either been stable or decreased in most countries over the same 25-year period.  This has contributed to a worldwide shift to lower mortality-incidence ratios between 1973-1977 and 1993-1997.  Mortality rate reductions have been attributed to better early detection, mass implementation of screening programmes and improved treatment.”

Paper: M D Althuis, J M Dozier, W F Anderson, S S Devesa and L A Brinton: ‘Global trends in breast cancer incidence and mortality 1973-1997’ Int J Epidemiol; 34: 405-412

The International Journal of Epidemiology is a key journal in the field of epidemiology and public health, published six times per year by Oxford University Press.  It is edited at the Department of Social Medicine, University of Bristol, which is a leading centre for epidemiology, health services research and public health in the UK and was one of only three to be awarded the top 5* grade in the 2001 Research Assessment Exercise.

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