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Inner workings

Cancer begins when genes which normally control cell division, growth and repair are damaged through mutation. These genes can then cause cells to grow and divide uncontrollably, destroying neighbouring healthy cells.

Once a cell has turned cancerous, it divides until a mass of cells forms a tumour. Diagnostic tests can quickly distinguish between malignant, or cancerous tumours and those that are benign, or harmless. As a malignant tumour progresses, cells or clumps of cells break off and spread, or metastasise, around the body via the lymphatic system and blood vessels.

 

The latest generation of treatments exploit our knowledge of what happens within cancerous cells. These target proteins and messenger chemicals - such as growth factors or enzymes - that the errant cells need to survive and grow.

 

Factoring in risk

 

Dozens of factors affect an individual’s risk of getting cancer.Smoking is the biggest single risk factor - with tobacco linked to about a third of all cancers.

Another clearly established risk factor is exposure to ionising radiation. This may be responsible for cancers in people living around chernobyl in Ukraine, Toikamura in Japan and for people working in nuclear power plants. Radiation may also have led to a high incidence of cancer in those who witnessed early nuclear tests or have been in contact with depleted uranium munitions, though a recent study contests this risk.

If everyone stopped smoking, cancer deaths could be cut by one-third, researchers estimate. Moves to protect people from passive smoking , in bars for example, are gaining ground in many industrialised countries.

Staying out of sunlight and using strong sunscreens could prevent hundreds of thousands of us from developing skin cancer worldwide annually. Foods rich in antioxidants and beneficial fatty acids found in olive oil- a key ingredient of the health Mediterranean diet- seem to protect against some cancers, although the findings are mixed.

Doctors can increasingly intervene directly to prevent cancers. For example, vaccines against hepatitis B could soon cut deaths from liver cancer. There are also preventive therapies - such as tamoxifen or the trial drug anastrazole - that interfere with the production of the hormone oestrogen, implicated in many breast cancers. Doctors believe that it could halve the rates of breast cancer in women with a family history of the disease.

All this means that, while hopes of total cure for cancer are still unrealistic, the disease is increasingly under control.

In the U.S. and other developed countries, cancer is presently responsible for about 25% of all deaths. On a yearly basis, 0.5% of the population is diagnosed with cancer. Click on the links to know more about each type of cancer.