Cancer is a leading cause of death worldwide and strongly related to lifestyle factors.
What causes cancer?
Cancer arises from one single cell. The transformation from a normal cell into a tumour cell is a multistage process, typically a progression from a pre-cancerous lesion to malignant tumours. These changes are the result of the interaction between a person’s genetic factors and three categories of external agents, including:
- physical carcinogens, such as ultraviolet and ionizing radiation
- chemical carcinogens, such as asbestos, components of tobacco smoke, aflatoxin (a food contaminant) and arsenic (a drinking water contaminant)
- biological carcinogens, such as infections from certain viruses, bacteria or parasites.
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WHO, through its cancer research agency, International Agency for Research on Cancer (IARC), maintains a classification of cancer causing agents.
Ageing is another fundamental factor for the development of cancer. The incidence of cancer rises dramatically with age, most likely due to a build up of risks for specific cancers that increase with age. The overall risk accumulation is combined with the tendency for cellular repair mechanisms to be less effective as a person grows older.
Cancer Key Facts:
- Cancer is a leading cause of death worldwide, accounting for 7.6 million deaths (around 13% of all deaths) in 2008 (1).
- Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms. One defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs. This process is referred to as metastasis. Metastases are the major cause of death from cancer.
- The number of global cancer deaths is projected to increase 45% from 2007 to 2030 (from 7.9 million to 11.5 million deaths), influenced by lifestyle factors and an increasing and aging global population. The estimated rise takes into account expected slight declines in death rates for some cancers in high resource countries. New cases of cancer in the same period are estimated to jump from 11.3 million in 2007 to 15.5 million in 2030.
- About 30% of cancer deaths are due to the five leading lifestyle and dietary risks: high body mass index, low fruit and vegetable intake, lack of physical activity, tobacco use, alcohol use.
- Lung, stomach, liver, colon and breast cancer cause the most cancer deaths each year.
- Tobacco use is an important lifestyle risk factor for cancer causing 22% of global cancer deaths and 71% of global lung cancer deaths.Lung cancer kills more people than any other cancer – a trend that is expected to continue until 2030, unless efforts for global tobacco control are greatly intensified.
- In European countries, cancer is the second largest cause of death after cardiovascular disease, and epidemiological evidence points to this trend emerging in the less developed world. This is particularly true in countries in “transition” or middle-income countries, such as in South America and Asia. Already more than half of all cancer cases occur in developing countries.
More than 40% of cancer deaths could be prevented by modifying or avoiding key lifestyle risk factors, including:
- Tobacco use – responsible for 1.8 million cancer deaths per year (60% of these deaths occur in low- and middle-income countries)
- Being overweight, obese or physically inactive – together responsible for 274 000 cancer deaths per year
- Harmful alcohol use – responsible for 351 000 cancer deaths per year
- Poor Nutrition and Unhealthy Diet
- Physical inactivity
Cancer prevention with lifestyle modification is an essential component of all cancer control plans because about 40% of all cancer deaths can be prevented.
References
Sagner et al 2017 Nature