What causes cancer?

Cancer is caused by accumulated damage to genes. Such changes may be due to chance or to exposure to a cancer causing substance.

The substances that cause cancer are called carcinogens. A carcinogen may be a chemical substance, such as certain molecules in tobacco smoke. The cause of cancer may be environmental agents, viral or genetic factors.

We should bear in mind, though, that in the majority of cancer cases we cannot attribute the disease to a single cause.

We can roughly divide cancer risk factors into the following groups:

  1. biological or internal factors, such as age, gender, inherited genetic defects and skin type
  2. environmental exposure, for instance to radon and UV radiation, and fine particulate matter
  3. occupational risk factors, including carcinogens such as many chemicals, radioactive materials and asbestos
  4. lifestyle-related factors.

Lifestyle-related factors that cause cancer include:

  • tobacco
  • alcohol
  • UV radiation in sunlight
  • some food-related factors, such as nitrites and poly aromatic hydrocarbons generated by barbecuing food).

Lifestyles can prevent cancer

Cancer causing factors related to work and living environments include:

  • asbestos fibres
  • tar and pitch
  • polynuclear hydrocarbons (e.g. benzopyrene)
  • Some metal compounds
  • Some plastic chemicals (e.g. Vinyl chloride)

Bacteria and viruses can cause cancer:

  • Helicobacter pylori (H. pylori, which causes gastritis)
  • HBV, HCV (hepatitis viruses that cause hepatitis)
  • HPV (human papilloma virus, papilloma virus, which causes changes eg. Cervical cells)
  • EBV (Epstein-Barr virus, the herpes virus that causes inflammation of the throat lymphoid)

Radiation can cause cancer:

  • ionising radiation (e.g. X-ray radiation, soil radon)
  • non-ionised radiation (the sun’s ultraviolet radiation)

Some drugs may increase the risk of cancer:

  • certain antineoplastic agents
  • certain hormones
  • medicines that cause immune deficiency

In 5 – 10 per cent of breast cancer genetic predisposition plays an important role in the emergence of the disease.

Cancer genetics

Genetic counselling on cancer

Sources

Joensuu, Heikki; Jyrkkiö, Sirkku; Kellokumpu-Lehtinen, Pirkko-Liisa; Kouri, Mauri; Roberts, Peter J. & Teppo, Lyly (toim.) (2013) Syöpätaudit. Helsinki: Kustannus Oy Duodecim.