MODEL RELEASED. Young cancer patient. Mother and child play cards in a cancer ward. The child has leukaemia, a cancer of the white blood cells. The mother is wearing a surgical mask and gown to prevent herself from infecting the child. The child is susceptible to infection because treatment for leukaemia involves anti-cancer drugs and radiotherapy. These have an adverse effect on a patient's immune system, making it necessary to keep the patient in a sterile environment. Such drugs also have side effects such as hair- loss. Leukaemia results from the uncontrolled proliferation of a class white blood cells known as polymorphonuclear leukocytes.