Background/Causes Of Cancer

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Although the vast majority of cancers are primarily caused by environmental factors, and the minority of cancers caused by genetic factors, it is likely all cancers have both a genetic and environmental component.

It is important to point out that the term causes does not mean that the particular factor will directly result in cancer developing. It means that the risk of cancer developing, as a result of exposure to a particular stimulus is more likely.


Common environmental causes of cancer include:

  • Tobacco smoking.
  • Diet (e.g: excessive alcohol consumption, unbalanced diet).
  • Being overweight (having a high BMI).
  • Infections — this does not mean cancer is infectious. It means that certain infections may increase the likelihood of certain cancers developing. For example, liver cancers may be caused by hepatitis B/C viruses or cervical cancer may be caused by the human papilloma virus.
  • Radiation (e.g: UV sunlight exposure or radioactivity).
  • Carcinogenic chemicals (carcinogenic = cancer causing) such as asbestos, benzene, powered nickel & cobalt and regular consumption of very hot drinks, such as tea.


There are some conditions, such as breast cancer, which have a genetic component. Individuals carrying a faulty BRCA gene are more likely than the general population to develop cancers such as ovarian or breast cancer.

Examples of carcinogenic stimuli that probably have both a strong genetic and environmental component include hormonal imbalances. For example, it is known that up-regulation of oestrogen levels in women increases the risk of them developing uterine cancer.

Another example of a genetic and environmental cause is age. In fact half of all cancer cases were diagnosed in adults aged 70+ between the years 2011-2013 [1].


  1. Cancer Research UK. Cancer incidence by age 2016. (accessed June 20, 2016).
  2. Cancer Research UK. The causes of cancer you can control. (accessed 04/07/2017).
  3. Cancer Research UK. Cancer statistics for the UK. (accessed 04/07/2017).
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