A doctor specialising in malignant diseases (cancers). Also known as a cancerologist. The word oncologist is most commonly used in England. Because of the complexity of these treatments and the number of types of cancer, radio-oncologists are distinguished from haemato-oncologists and medical oncologists who are specialised in chemotherapy. In order to treat a patient, the oncologist, radio-oncologist, surgeon and specialist in the organ affected (for example the urologist for a prostate tumour) usually work together (see inter-disciplinarity).