good to know says: Cancer is a disease which many people now survive. There are more than 200 different types of cancer, but they all start in the same way, with one abnormal cell. Many cancers have no obvious cause and happen 'out of the blue'. But there are recognised risk factors which can increase your chances of developing it. They include smoking, exposure to chemicals like asbestos, eating too much fatty food and drinking too much alcohol. Some cancers also have a strong genetic link, particularly childhood cancers. But most cancers develop in older people.
For a full medical explanation of the causes, symptoms and treatments of cancer from patient.co.uk read on
Cancer is a disease of the cells in the body. The body is made up from millions of tiny cells. Different parts of the body such as organs, bones, muscles, skin, and blood are made up from different specialised cells. All cells have a centre called a nucleus which contains genes made from DNA. The genes control the functions of the cell.
There are many different types cells in the body, and many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply 'out of control'. See the leaflet called 'What is Cancer' for more details.
Each cancer is thought to first start from one abnormal cell. What seems to happen is that certain vital genes which control how cells divide and multiply are damaged or altered. This makes the cell abnormal. If the abnormal cell survives it may multiply 'out of control' into a malignant tumour.
We all have a risk of developing cancer. Many cancers seem to develop for no apparent reason. However, certain risk-factors are known to increase the chance that one or more of your cells will become abnormal and lead to cancer. Risk factors include the following:
A carcinogen is something (chemical, radiation, etc) which can damage a cell and make it more likely to turn into a cancerous cell. As a general rule, the more the exposure to a carcinogen, the greater the risk. A list of known and suspected chemical carcinogens can be found at http://physchem.ox.ac.uk/MSDS/carcinogens.html
Well-known examples include:
The older you become, the more likely that you will develop a cancer. This is probably due to an accumulation of damage to cells in the body over time. Also, the body's defences and resistance against abnormal cells may become less good as you become older. For example, the ability to repair damaged cells, and the immune system which may destroy abnormal cells, may become less efficient with age. So, eventually one damaged cell may manage to survive and multiply 'out of control' into a cancer. Most cancers develop in older people.
Diet and other lifestyle factors may increase or decrease the risk of developing cancer. For example:
Radiation is a carcinogen. For example, exposure to radioactive materials and nuclear 'fallout' can increases the risk of leukaemia and other cancers. Too much sun exposure and sunburn (radiation from UVA and UVB) increase your risk of developing skin cancer.
The larger the dose of radiation, the greater the risk of developing cancer. But note: the risk from small doses such as from a single X-ray test is very small.
Some viruses are linked to certain cancers. For example, people with persistent infection with the hepatitis B virus or the hepatitis C virus have an increased risk of developing cancer of the liver. But, most viruses and viral infections are not linked to cancer.
People with a poor immune system have an increased risk of developing certain cancers. For example, people with AIDS, or people on immunosuppressive therapy.
Some cancers have a strong genetic link. For example, in certain childhood cancers the abnormal gene or genes which may trigger a cell to become abnormal and cancerous are inherited. Other types of cancer may have some genetic factor which is less clear-cut. It may be that in some people their genetic make-up means that they are less resistant to the effect of carcinogens or other factors such as diet.
Not everybody who comes into contact with a carcinogen or has an unhealthy lifestyle will develop cancer. For example, not all smokers develop cancer of the lung. In fact, we are all probably exposed to low doses of carcinogens a lot of the time.
The body has certain mechanisms which may protect us from developing cancer. For example, it is thought that many cells which are damaged by carcinogens can repair themselves. Also, the body's immune system may be able to destroy some types of abnormal cells before they multiply into a tumour. Perhaps one carcinogen may only damage one gene, and two or more genes may need to be damaged or altered to trigger the cells to multiply 'out of control'.
In many cases it is likely that a combination of factors such as genetic make-up, exposure to a carcinogen, age, diet, the state of your immune system, etc, play a part to trigger a cell to become abnormal, and allow it to multiply 'out of control' into a cancer.
Cancer Research UK
Their website, Cancer Help, provides detailed facts about cancer.
© EMIS and PIP 2006 Updated: February 2006