Worldwide breast and lung cancer cases have doubled since 1975, according to a new report published today by Cancer Research UK.
The increase in the number of cases reflects the world’s growing population and the fact that people are living longer in all parts of the globe. The proportion of the world’s population aged 60 or over currently stands at 10 per cent, but is expected to more than double to 22 per cent by 2050. Most forms of cancer are linked to age: the older you are, the higher your risk, so older populations generally have more cases of cancer.
The good news is that rates of stomach cancer, the most common type of cancer in 1975, are falling in association with improved home hygiene and food preservation. And cervical screening programmes in developed countries have significantly reduced the number of women being diagnosed with cervical cancer, although cases are still rising in the fast-growing populations of developing countries.
Even though overall cancer incidence is rising, UK cancer mortality rates are falling thanks to earlier diagnosis and better treatment.
A team of Cancer Research UK statisticians analysed global cancer information from the IARC GLOBOCAN 2002 database1. Their report compares incidence and mortality rates in different regions of the world, and describes changes in the numbers of people being diagnosed between 1975 and 2002.
The report also summarises evidence of smoking habits in different regions of the globe. It suggests that over the coming decades, developing countries will have to cope with soaring rates of lung cancer, already the most commonly diagnosed cancer in the world.
Ruth Yates, Statistical Information Team Manager at Cancer Research UK, says: “Knowing which parts of the world have fewer cases of particular cancers can help us identify cultural factors, such as diet, smoking and drinking, that affect the risk of getting the disease.
“However, age explains most of the differences in risk. As the world’s population gets older, the number of people diagnosed with cancer will continue to rise.”
Over 1.1 million cases of breast cancer are now diagnosed across the world each year. This compares to around half a million cases in 1975. Most of the increase is accounted for by the increased life expectancy among women worldwide, together with the world’s growing population – around 4 billion in 1975, it is currently estimated to be 6.3 billion.
In relation to lung cancer, smoking is a far more important risk factor than age. Lung cancer has become the most commonly diagnosed cancer in the world, with approximately 1.4 million new cases every year compared to fewer than 600,000 in 1975. Most of these are thought to be smoking-related.
The message from the developed world is that lung cancer rates follow smoking rates. Incidence of the disease tends to peak about 20 years after the proportion of people smoking peaks. Countries such as the UK, where smoking has declined among men and has peaked among women, are seeing big falls in the numbers of people being diagnosed with lung cancer.
But in regions of the world where the prevalence of smoking has increased – eastern Africa, central America and southeast Asia in particular – there will be big increases in the numbers of people diagnosed with lung cancer over the next twenty years.
Professor John Toy, Cancer Research UK’s Medical Director, says: “These statistics show that cancer is still essentially a major disease of the developed world. Only four per cent of deaths in Africa are due to cancer, compared to 19 per cent in Europe. The developing world can learn from past mistakes: tackling the smoking habit, for example, would minimise future lung cancer cases and substantially reduce the future cancer burden in developing countries.
“Although these figures show a persistent increase in the number of people in the world being diagnosed with cancer, developing and refining new treatments will continue to improve the chances of surviving the disease. Already, thanks to such research, many more people diagnosed with cancer in 2005 will survive compared to those diagnosed in 1975.”
- Ferlay et al. GLOBOCAN 2002: Cancer Incidence, Mortality and Prevalence Worldwide. IARC Cancerbase No.5 version 2.0. IARCPress, Lyon, 2004. Link.
Not all types of cancer are on the increase. Stomach cancer was the world’s most commonly diagnosed cancer in 1975, but it has fallen to fourth (after lung, breast and bowel cancer), largely because of lifestyle changes in developed countries.
Stomach cancer is related to diet and a bacterium called Helicobacter pylori. Better hygiene and reduced household overcrowding have lowered the prevalence of H. pylori, which, combined with improved food preservation and storage, has reduced the number of cases in the West. For example, now only four per cent of cancers in the UK are stomach cancer.
Cervical cancer tends to affect younger women than other cancers and is less sensitive to the ageing population effect. Incidence and mortality rates have both fallen substantially in developed nations with cervical screening programmes, such as the UK.
Cancer Research UK
Cancer Research UK’s vision is to conquer cancer through world-class research.
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For further information about Cancer Research UK’s work or to find out how to support the charity, please call +44 20 7009 8820 or visit Cancer Research UK.
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