The Top 5 Causes of Cancer by Major Risk Factors

  Cancer Cause Proportion of Risk
1 Poor diet & nutrition 30%
2 Tobacco 16%
3 Infections 8%
4 Occupational exposures 5%
5 Environmental pollution 2%
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  1. All cancers involve the malfunction of genes that control cell growth, division, and death. However, most of the genetic abnormalities that affect cancer risk are not hereditary, but instead result from damage to genes (mutations) that occur throughout one's lifetime. Damage to genes may be due to internal factors, such as hormones or the metabolism of nutrients within cells, or external factors, such as tobacco, chemicals, and sunlight. (These non-hereditary mutations are called "somatic mutations"). It is estimated that 5%-10% of all cancers are strongly hereditary, meaning that individuals who inherit a specific genetic alteration have a very high risk of developing a particular cancer. It is thought that many cancers result from a combination of hereditary and environmental factors. (a.)
  2. Lung cancer has been the most common cancer in the world for several decades, and by 2008, there were an estimated 1.61 million new cases, representing 12.7% of all new cancers. It was also the most common cause of death from cancer, with 1.38 million deaths (18.2% of the total). The majority of the cases now occur in developing countries (55%). Lung cancer is still the most common cancer in men worldwide (1.1 million cases, 16.5% of the total), with high rates in Central-Eastern and Southern Europe, North America and Eastern Asia. Very low rates are still estimated in Middle and Western Africa. According to the United States Environmental Protection Agency; smoking, radon, and secondhand smoke are the leading causes of lung cancer. Smoking causes an estimated 160,000 cancer deaths in the U.S. every year. And the rate among women is rising. On January 11, 1964, Dr. Luther L. Terry, then U.S. Surgeon General, issued the first warning on the link between smoking and lung cancer. Lung cancer now surpasses breast cancer as the number one cause of death among women in the United States. Radon is the number one cause of lung cancer among non-smokers, according to EPA estimates. Overall, radon is the second leading cause of lung cancer. Radon is responsible for about 21,000 lung cancer deaths every year in the U.S. About 2,900 of these deaths occur among people who have never smoked. (a.), (d.)
  3. In females, lung cancer incidence rates are generally lower, but, worldwide, lung cancer is now the fourth most frequent cancer of women (513 000 cases, 8.5% of all cancers) and the second most common cause of death from cancer (427 000 deaths, 12.8% of the total). The highest incidence rate is observed in North America (where lung cancer it is now the second most frequent cancer in women), and the lowest in Middle Africa (15th most frequent cancer). Because of its high fatality (the ratio of mortality to incidence is 0.86) and the lack of variability in survival in developed and developing countries, the highest and lowest mortality rates are estimated in the same regions, both in men and women. (a.)
  4. According to GLOBOCAN, an estimated 12.7 million new cancer cases and 7.6 million cancer deaths occurred in 2008. Cancer is neither rare anywhere in the world, nor confined to high-resource countries. "Striking differences in the patterns of cancer from region to region are observed," Dr. Christopher Wild, IARC Director, stated: "Cervix and liver cancers are much more common in developing regions of the world, whereas prostate and colorectal cancers are more common in developed regions." (b.)
  5. A higher proportion of the cancer burden occurs in less developed regions of the world, both in terms of cancer incidence (56% of new cancer cases in 2008 occur within developing regions) and cancer mortality (63% of cancer deaths). The most commonly diagnosed cancers worldwide are lung (1.61 million, 12.7% of the total), breast (1.38 million, 10.9%) and colorectal cancers (1.23 million, 9.7%). The most common causes of cancer death are lung (1.38 million, 18.2% of the total), stomach (0.74 million, 9.7%) and liver cancers (0.69 million, 9.2%). (b.)
Top 5 facts sources:
  1. The American Cancer Society. (2007). "Global Cancer Facts & Figures 2007" (pages 1-4). Retrieved December 9th, 2010.
  2. GLOBOCAN. (2008). "Globocan 2008 Cancer Fact Sheet". Retrieved Dec, 2010.
  3. International Agency for Research on Cancer. (2010). Press release: "IARC launches the definitive cancer statistics resource GLOBOCAN 2008". Retrieved Dec, 2010.
  4. United States Environmental Protection Agency. "Health Risks" Retrieved Dec, 2010. Web page:
Tags: Health Statistics, Cancer statistics

Sources:  American Cancer Society: The Cancer Atlas, 2006.

List Notes: Data is for the year 2006.
Causes of Cancer by Major Risk Factors

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