Chemotherapy works by damaging rapidly growing cells. Because cancer is fast growing, chemotherapy is very effective against these cells. However, in addition to damaging cancer cells, chemotherapy may also damage other fast growing cells, including the cells in the bone marrow. Because bone marrow cells produce blood cells, chemotherapy can cause a period of low blood counts 7 to 14 days (sometimes longer) after it is given.
The length of time blood counts remain low is determined by the type of drug, the disease, and the individual. It is different for every child. The point at which blood counts are at their lowest is called the nadir.
Children may have a low red blood cell count, called anemia; a low platelet count, called thrombocytopenia; and/or a low white blood cell count, called neutropenia.
Some children with cancer need to receive transfusions of specific parts of blood, such as red blood cells or platelets. Blood transfusions may be given to control the low blood cell counts or bleeding that sometimes results from chemotherapy.
Each person has a specific blood type. Blood tests, called blood typing and cross-matching, are done to determine your child’s blood type. If your child needs a blood transfusion, the risks and benefits will be discussed with you beforehand and you will need to sign a consent.