Chemotherapy is the use of drugs to treat an illness, radiotherapy is the use of radiation in treatment. Strictly speaking chemotherapy is the use of drugs in any illness but in recent years the word has come to be associated mainly with the drug treatment of cancer. There are more than a hundred different drugs available for cancer treatment and these fall into two main groups: cytotoxics and hormones. Cytotoxics are drugs which act directly on cancer cells to destroy them. They are used in a wide variety of different cancers. Hormones are drugs which are suitable for a limited number of cancers (particularly breast and prostate tumours) where changes in the hormone levels in the blood can influence the growth of the disease. Not everyone who develops a cancer will need chemotherapy, the choice of treatment varies with different types of cancer. Radiotherapy is mainly, but not exclusively, used for cancer treatment. Again not everyone with cancer will need radiotherapy. Radiotherapy uses ionising radiation to kill cancer cells. The treatment is usually given by machines which produce a beam of high energy x-rays. The patient then lies on a bed under the machine and the beam is directed at the site of the cancer. The treatment is usually given as an out-patient. For some tumours radiotherapy may be given in the form of radioactive pellets or seeds placed close to or into the cancer, this is called brachytherapy.