chemotherapy In cancer:- How chemotherapy works

How chemo kills cancer cells

Chemotherapy damages dividing cells. You can have chemotherapy either as an injection into the bloodstream or have it as tablets or capsules. The drugs circulate all round the body in the bloodstream and damage any cells that are dividing. Body tissues are made of billions of individual cells. Once we are fully grown, most of the body's cells don't divide much. They spend most of their time in a resting state and only divide if they need to repair damage. When cells divide they split into two, identical new cells.

So, where there was 1 cell, there are now 2 and these then divide to make 4 and then 8 and so on. And cancer cells divide much more often than most normal cells. This is how tumours grow and form lumps. Cells in the process of dividing are more at risk of being damaged by chemotherapy. Chemotherapy damages part of the control centre inside each cell that makes cells divide. Or it interrupts the chemical processes involved in cell division. The damaged cells then die.

There is more detailed information about how normal cells grow and about how cancer cells differ from normal cells in the about cancer section of CancerHelp UK.

How chemotherapy kills dividing cells
Chemotherapy damages cells as they divide. In the centre of each living cell is a dark blob, called the nucleus. The nucleus is the control centre of the cell. It contains chromosomes, which are made up of genes. These genes have to be copied exactly each time a cell divides into 2 to make new cells.

Chemotherapy damages the genes inside the nucleus of cells. Some drugs damage cells at the point of splitting. Some damage them while they are busy making copies of all their genes before they split. Cells that are at rest (most normal cells, for instance) are much less likely to be damaged by chemo. You may have a combination of different chemotherapy drugs. The combination will include chemo drugs that damage cells at different stages in the process of cell division. With more than one type of drug, there is more chance of killing more cells.

The fact that chemo drugs kill dividing cells helps to explain why chemotherapy causes side effects. It affects healthy body tissues where the cells are constantly growing and dividing. The skin, bone marrow, hair follicles and lining of the digestive system are examples of these. Your hair is always growing. Your bone marrow is constantly producing blood cells. The cells of your skin and the lining of your digestive system are constantly renewing themselves. These tissues have dividing cells and they can be damaged by chemotherapy.

But, normal cells can replace the healthy cells that are damaged by chemotherapy. So the damage to healthy cells doesn't usually last. Most side effects disappear once your treatment is over, and some only happen during the days while you are actually having the drugs (for example, sickness or diarrhoea). The section on chemotherapy side effects explains this in more detail.

How well chemotherapy works
The chance of the chemotherapy curing your cancer depends on the type of cancer you have


With some types of cancer, most people are cured by chemotherapy
With other types of cancer, fewer people are completely cured
Examples of cancers where chemotherapy works very well are testicular cancer and Hodgkin's lymphoma.

With some cancers, chemotherapy can't cure the cancer on its own. But it can help in combination with other types of treatment. Many people with breast or bowel cancer, for example, have chemotherapy after surgery to help lower the risk of the cancer coming back.

With some cancers, if a cure is unlikely, your doctor may still suggest chemotherapy to


Shrink the cancer
Relieve your symptoms
Give you a longer life by controlling the cancer or putting it into remission
What remission means
Remission is a word doctors often use when talking about cancer or leukaemia. It means there is no sign of the cancer. Doctors can be reluctant to say that a cancer is 'cured' because some cancers can come back years later. The more time that goes by, the less likely it is that a cancer will come back. But there is still that small chance. So doctors use the word 'remission'. You may hear your doctor talk about complete remission and partial remission.
Complete remission means that the cancer or leukaemia can't be detected on scans, X-rays, or blood tests etc.
Partial remission means the treatment has killed some of the cells, but not all. The cancer has shrunk, but can still be seen on scans and doesn't appear to be growing.. The treatment may have stopped the cancer from growing. Or made it smaller so that other treatments are more likely to help, such as surgery or radiotherapy.