Chemotherapy drugs can stop cancer cells dividing and reproducing themselves. As the drugs are carried in the blood, they can reach cancer cells anywhere in the body. They are also taken up by some healthy cells. Healthy cells can repair the damage caused by chemotherapy, but cancer cells cannot and so they eventually die.

Different chemotherapy drugs damage cancer cells in different ways. If a combination of drugs is used, each drug is chosen because of its different effects.

Unfortunately, as the chemotherapy drugs can also affect some of the healthy cells in your body, they can cause unpleasant side effects. However, damage to the healthy cells is usually temporary and most side effects will disappear once the treatment is over.

Healthy cells in certain parts of the body are especially sensitive to chemotherapy drugs; these parts of the body include:

• the bone marrow (which makes blood cells)
• the hair follicles
• the lining of the mouth
• the digestive system.

Chemotherapy is usually given as a series of sessions of treatment. Each session is followed by a rest period. The session of chemotherapy and the rest period is known as a cycle of treatment. A series of cycles makes up a course of treatment.

Each session of chemotherapy destroys more of the cancer cells, and the rest period allows the normal cells and tissues to recover.