Part I

By Dr Anirban Banerjee, MS, MRCS (Consultant Surgeon)
What is cancer?

Cancer is a disease of the cells (the building blocks of the body). There are many different types of cell in the body and different types of cancer can arise from different types of cell. What is common in all types of cancer is that the cancer cells are abnormal and multiply out of control. Some cancers are more serious than others and some have a better outlook.
Normal body cells

The body is made up of millions of tiny cells. Different parts of the body such as organs, bones, muscles, skin, and blood are made up of different specialized cells. All cells have a centre called a nucleus. The nucleus in each cell contains thousands of genes which are made up of a chemical called DNA. The genes are like ‘codes’ which control the functions of the cell. Most types of cell in the body divide and multiply from time to time. As old cells wear out or become damaged, new cells are formed to replace them.
Abnormal cells

Sometimes a cell becomes abnormal. Lots of abnormal cells may develop from the original abnormal cell. These cells do not know when to stop multiplying. A group of abnormal cells may then form. If this group of cells gets bigger, it becomes a large clump of abnormal cells called a tumour.
Tumours

A tumour is a lump or growth of tissue made up from abnormal cells. Tumours are divided into two types –benign and malignant.
Benign tumours

These may form in various parts of the body. Benign tumours grow slowly, and do not spread or invade other tissues. They are not cancerous and are not usually life-threatening. They often do no harm if they are left alone. However, some benign tumours can cause problems.
Malignant tumours (cancers)

Malignant tumours tend to grow quite quickly, and invade nearby tissues and organs which can cause damage. Tumours normally develop in one original site: the primary tumour. Malignant tumours may also spread to other parts of the body to form secondary tumours (metastases). This happens if some cells break off from the primary tumour and are carried in the bloodstream or lymph channels to other parts of the body. These secondary tumours may then grow, invade and damage nearby tissues, and spread again.
What causes cancer?

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.  The risk factors include the following:
Chemical carcinogens

A carcinogen is something (chemical, radiation, etc) that 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. Well known examples include:
Tobacco smoke – smokers are more likely to develop cancer of the lung, mouth, throat, oesophagus, bladder and pancreas. Smoking is thought to cause about a quarter of all cancers. About 1 in 10 smokers die from lung cancer. The more heavily you smoke, the greater the risk. If you stop smoking, your risk goes down considerably.
Workplace chemicals – such as asbestos, benzene, formaldehyde, etc – If you have worked with these without protection you have an increased risk of developing certain cancers.
Age – most cancers develop in older people. Cancer risks increase with age.
Life style factors

Diet and other lifestyle factors can alter the risk of developing cancer. For example:

*Eating a lot of fruit and vegetables reduces the risk of developing certain cancers. The exact way in which they protect against cancer is not fully understood. These foods are rich in vitamins and minerals, and also contain chemicals called anti-oxidants. They may protect against damaging chemicals that get into the body. We should all eat at least five portions of fruit and vegetables per day.

*Eating too much fatty food possibly increases the risk of developing certain cancers.

*The risk of developing certain cancers is increased by obesity, lack of regular exercise, and drinking a lot of alcohol.
Radiation

Radiation is a carcinogen. For example, exposure to radioactive materials and nuclear fallout can increase the risk of developing leukaemia and other cancers. Excessive sun exposure and sunburn (radiation from UVA and UVB) increase the risk of skin cancer. The larger the dose of radiation, the greater the risk of developing cancer. But  the risk from small doses such as from a single X-ray test is very small.
Infection

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. Another example is the link between the human papilloma virus (HPV virus) and cervical cancer. Most (possibly all) women who develop cervical cancer have been infected with a strain (sub-type) of the HPV virus at some point in their life. However, most viruses and viral infections are not linked to cancer.
Immune system

People with a poor immune system have an increased risk of developing certain cancers, for example, people with AIDS, or people on immuno-suppressive therapy.
Your genetic make-up

Some cancers have a strong genetic link. For example, in certain childhood cancers the abnormal gene or genes that may trigger a cell to become abnormal and cancerous is inherited. Other types of cancer may have some genetic factor which is less clear cut.

To be continued