There are about 200 different types of cancer affecting all the different body tissues. What affects one body tissue may not affect another. For example, tobacco smoke that you breathe in may help to cause lung cancer. Over exposing your skin to the sun could give you a melanoma on your leg. But the sun won't give you lung cancer and smoking won't give you melanoma.
Apart from infectious diseases, most illnesses are 'multifactorial'. Cancer is no exception. Multifactorial means that there are many factors involved. In other words, there is no single cause for any one type of cancer.
Carcinogens
A 'carcinogen' is something that can help to cause cancer. Tobacco smoke is a powerful carcinogen. But not everyone who smokes gets lung cancer. So there must be other factors at work.
Age
Most types of cancer become more common as we get older. This is because the changes that cause a cell to become cancerous in the first place take a long time to develop.
Genetic make up
There have to be a number of genetic mutations within a cell before it becomes cancerous. Sometimes we are born with one of these mutations already. This does not mean we will get cancer. But with one mutation from the outset, it makes it more likely statistically that we will. Doctors call this 'genetic predisposition'.
The immune system
People who have problems with their immune systems are more likely to get some forms of cancer. This group includes people who
- Have had organ transplants and take drugs to suppress their immune systems to stop organ rejection
- Have AIDS
- Are born with rare medical syndromes which affect their immunity
Diet
Cancer experts estimate that changes to our diet could prevent about one in three cancer deaths in the UK. In the western world, many of us eat too many animal fats and not enough fresh fruit and vegetables. This type of diet is known to increase your risk of cancer. But how exactly we should alter our diets is not clear.
Viruses
Viruses can help to cause some cancers. But this does not mean that these cancers can be caught like an infection. What happens is that the virus can cause genetic changes in cells that make them more likely to become cancerous.
These cancers and viruses are linked:
- Cervical cancer and the genital wart virus, HPV
- Primary liver cancer and the Hepatitis B virus
- T cell leukaemia in adults and the Human T cell leukaemia virus
