Cancer in the World : mechanisms, causes, trends, treatments – The 2008 Report of the WHO.

 The Word Cancer Report 2008 – Excerpts from the introduction and from some                                               chapter’s summaries made by GreenFacts

The World Cancer Report 2008 (267 pp) provides a unique and comprehensive global overview global view of cancer and documents about many important features of the global situation of cancer. It presents information on cancer etiology, diagnosis, causes and mechanisms or prevention concisely, clearly outlining the growing public health crisis. It describes also most important cancers site by site.

The World Cancer Report can be ordered at :

http://apps.who.int/bookorders/anglais/detart1.jsp?sesslan=1&codlan=1&codcol=76&codcch=26#

 About the mechanisms of cancer

Cancer is described in the Report as a multi- step process in which cells undergo metabolic and behavioural changes, leading them to proliferate in an excessive and untimely way. These changes arise through modifications in mechanisms that control cell proliferation and lifespan, relationships with neighbouring cells, and capacity to escape the immune system.

Modifications that lead to cancer, says the report, include genetic changes that modify the DNA sequence.  Other  changes in the programme of cells leading to cancer is the modification of the conformation of chromatin, the structure that wraps up DNA in the cell nucleus and regulates its access by DNA reading, copying and repair machineries. Such changes are called “epigenetic”. Among the 23 000 or so genes that constitute the human genome, a few hundred are commonly targeted by genetic or epigenetic changes. These genes are parts of networks of genes that regulate cell division, differentiation and life span.

About the causes of cancer

In 2008, the report states that there were 12.4 million new cancer cases and 7.6 million cancer deaths worldwide. There are several clearly identified causes of cancer and several strategies that can lead to reductions in cancer incidence and mortality. Currently, the most common forms of cancer differ between high-income countries and the remainder. In high-income countries, cancers of the lung, breast, prostate and colorectum dominate, and one third of cancers are caused by tobacco use and 10% by chronic infection. Cancer control priorities include tobacco control, (high-tech) screening for small tumours, and curative treatment.  In low-resource and medium-resource countries, cancers of the stomach, liver, oral cavity, and cervix dominate.

About the declining trend in cancer mortality rates In Europe and the US.

The report says that during the lifespan of the ‘Europe Against Cancer’ program, cancer mortality in the (then-15) Member States of the European Union (EU) had started to decline; the estimated number of deaths in 2000 was 9.0% fewer than expected on the basis of application of the age-specific mortality rates from the mid-1980s to the 2000 population. When almost all the mortality data for 2000 eventually available, there were in the EU,  9.5% fewer death than expected. These declines have subsequently been confirmed.

The ‘Annual Report to the Nation on the Status of Cancer, 1975-2005′, cited by the World Cancer Report  says that in the US, cancer death rates have decreased by 18.4% among men and 10.5% among women since the early 1990s. The cancer death rate continues to go down and now cancer incidence—the rate at which new cancers are diagnosed also—appears to be dropping. Cancer death rates for both sexes combined declined about 1.8% per year from 2002 through 2005, almost double the 1.1% per year decrease seen from 1993 through 2002.  Cancer death rates in the United States declined for 10 of the 15 most common causes of cancer death among both men and women, but increased for a few individual cancers, such as esophageal and bladder cancers among men, pancreatic cancers in women, and for cancers of the liver in both. The decline in cancer incidence was largely due to declines in the most common cancers: lung, colorectal and prostate cancer for men and breast and colorectal cancer for women.

 About cancer and occupational exposure

Twenty-nine occupational agents, as well as 15 exposure circumstances are carcinogenic to humans. Exposure is still widespread for several important carcinogens such as asbestos, polycyclic aromatic hydrocarbons, heavy metals and silica. The burden of occupational cancer among exposed subjects may be substantial. Prevention of occupational cancer is feasible and has taken place in industrialized countries during recent decades. Limited data on occupational cancer risk are available from low-income countries

About the limited contribution of environmental pollution to the world’s cancer burden.

Environmental pollution which contributes to the world’s cancer burden in a limited way, concludes the report. Many known, probable and possible carcinogens can be found in the environment, and all people carry traces of these pollutants in their bodies. Some environmental pollutants are widely dispersed, and others are concentrated in small geographic areas. There are wide disparities in exposure, and pollution levels can be high in newly industrialised countries with less stringent regulations. Much environmental pollution can be prevented.

About other causes of cancer

Chronic inflammation has been associated with excess risk of lung cancer, mesothelioma, oesophageal, colorectal, bladder and several other cancers. Chronic pancreatitis has been related to a gross excess risk of pancreatic cancer;  Subjects with cirrhosis have an over tenfold excess risk of primary liver cancer and diabetes is associated with excess risk of endometrial, colorectal, liver and possibly pancreatic cancer. >>Excess cancer risk has been reported in subjects treated with chemotherapy, radiotherapy, HRT , phenacetin and selective other drugs.

The World Cancer Report is edited by Peter Boyle and Bernard Levin,  World Health Organization

A related document from The WHO :

The World Health Organization’s fight against cancer: strategies that prevent, cure and care

This brochure gives a dynamic glimpse of the many cancer control activities WHO performs. Each activity fits within the four broad approaches WHO takes to fight cancer: Prevention, Cure, Care and Manage. WHO’s intensive efforts have produced dozens of strategies, recommendations and technical programmes to combat cancer, prevent needless deaths and provide appropriate care for the terminally ill. WHO has consolidated these tools for countries in a framework known as the national cancer control programme, which focuses government attention and services on all facets of the fight against cancer.

see : http://www.who.int/cancer/publications/en/

See also some of the GreenFacts Digests :

on Alcohol and health (summary of a IARC document) : http://www.greenfacts.org/en/tobacco/index.htm

on tobacco smoking (summary of a WHO document)  http://www.greenfacts.org/en/alcohol/index.htm

on arsenic (summary of an IPCS document) :  http://www.greenfacts.org/en/arsenic/index.htm

on the consequences of the Chernobyl catastrophy (a summary of the Chernobyl Forum Report ) :

http://www.greenfacts.org/en/chernobyl/index.htm

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