Chemotherapy is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. The drugs are usually given intravenously (by injection into a vein), and as a course of treatment lasting a few days. This is followed by a rest period of a few weeks which allows the body to recover from any side effects of the treatment. The number of courses that are given depend on the type of cancer and how well it is responding to the drugs. Treatment is usually given as an out-patient.