Endorsed by the European Oncology Nursing Society

What causes cancer?

What causes cancer? image

Cancer typically occurs when cells in a part of the body become abnormal, and keep on dividing to make more abnormal cells. (For more on this, see the article )1 It is caused by changes to genes that control how cells grow; these changes may include mutations, which can be inherited or acquired.2

Lifestyle behaviours such as the following can increase your risk:

  • Excessive alcohol consumption:
    • More than 1 alcoholic drink per day for females and more than 2 alcoholic drinks per day for males3,4,5
  • One drink is 148 mL of wine or 355 mL of beer or 44 mL of spirits5 
  • Unhealthy diet:
    • Eating a lot of processed or red meat can increase the risk of certain cancers6
    • A high-salt diet may also be linked to an increased risk of certain cancers6
  • Smoking3
  • Too much exposure to sunlight or UV radiation, e.g. due to sunbathing3,7

Changes may also be brought about by exposure to environmental risk factors such as:

  • Exposure to cancer-causing substances (e.g. asbestos)3,8
  • Exposure to high-energy radiation
    • For example from a nuclear power plant or from atomic weapon testing3,9

Some physical conditions may make you more prone to cancer, for instance:

  • Hormones
    • Increased exposure to high levels of oestrogen and progesterone, e.g. if you start your periods early or have a late menopause, or you had your first full-term pregnancy at a late age, has been linked to an increased risk of breast cancer3,10,11
  • Infection
    • Certain viruses may increase your risk of cervical cancer. For example, certain types of human papillomavirus (HPV) may increase your risk of cervical cancer3,12
  • Obesity3
  • Obesity is defined as a body mass index (BMI) of 30 or above13

Mutations in genes that are passed down through families can increase your risk of developing certain cancers.14

Your risk is determined by a complex combination of genetics, environmental factors, and lifestyle factors.15 This can explain why some people with several risk factors never develop cancer, while others with no known risk factors do develop cancer.14



  1. Cancer.org. What Is Cancer?
  2. The National Cancer Institute. The Genetics of Cancer. Accessed April 2016.
  3. The National Cancer Institute. Risk factors for cancer. Accessed April 2016.
  4. The National Cancer Institute. Alcohol. Accessed April 2016.
  5. Mayo Clinic. Alcohol: If you drink, keep it moderate Accessed April 2016.
  6. Cancer Research UK. How healthy eating prevents cancer Accessed April 2016.
  7. The National Cancer Institute. Sunlight. Accessed April 2016.
  8. The National Cancer Institute. Substances. Accessed April 2016.
  9. The National Cancer Institute. Radiation. Accessed April 2016.
  10. The National Cancer Institute. Hormones. Accessed April 2016.
  11. The National Cancer Institute. Reproductive History. Accessed April 2016.
  12. The National Cancer Institute. Infectious Agents. Accessed April 2016.
  13. NHS. Obesity. Accessed April 2016.
  14. The National Cancer Institute. Genetic Testing. Accessed April 2016.
  15. Cancer Research UK. Causes of cancer can be prevented. Accessed April 2016.