Therapy Class Review: Blood Modifiers

Todd Cooperman, PharmD, RPh; and Russel Allinson, RPh, MS
Published: Wednesday, Mar 02, 2011
Disease Overview

In reviewing the therapeutic category of blood modifiers, there are 3 areas of focus: red blood cells (erythropoiesis growth factors, ie, Procrit, Epogen); white blood cells (myeloid growth factors, ie, Neupogen, Leukine, Neulasta); and platelets (thrombopoietic growth factors, ie, Neumega).All of these products work by stimulating bone marrow to produce more cells.

Anemia is a condition that occurs when the blood does not contain enough red blood cells that carry oxygen from the lungs to the body's tissues. In a healthy person, the body sends signals to the bone marrow to create more red blood cells whenever it needs more oxygen. Erythropoietin, which is produced in the kidney, is the signal that stimulates the bone marrow to produce red blood cells. When the body does not produce enough erythropoietin, fewer red blood cells are produced and therefore less oxygen is delivered to the body.1

Certain diseases, such as cancer and chronic kidney failure, are related to anemia. Cancer patients undergoing chemotherapy often suffer from anemia because chemotherapy attacks not only cancerous cells but also other cells in the body, including red blood cells. Because erythropoietin is produced in the kidneys, in patients who have kidney disease and whose kidney function is reduced, less erythropoietin is produced, which leads to reduced production of red blood cells.1

Neutropenia is a condition defined by an abnormally low number of neutrophils. Neutrophils serve as the major defense of the body against acute bacterial and certain fungal infections. Neutrophils usually constitute about 45% to 75% of all white blood cells in the bloodstream. When the neutrophil count falls below 1000 cells per microliter of blood, the risk of infection increases somewhat; when it falls below 500 cells per microliter, the risk of infection increases greatly. Without the key defense provided by neutrophils, an individual has problems controlling infections and could be at risk of dying from an infection. Neutropenia can be caused by many things: radiation therapy, chemotherapy, autoimmune disorders, viral infections, leukemia, and aplastic anemia, to name a few.2

Thrombocytopenia is the term for a reduced platelet (thrombocyte) count. It happens when platelets are lost from the circulation faster than they can be replaced from the bone marrow. Platelets play a very important role in stopping bleeding and beginning the repair of injured blood vessels.

Normally, a person has anywhere from 150,000 to 450,000 platelets per microliter of circulating blood. Because each platelet lives for only about 10 days, the platelet supply is continually renewed by production of new platelets. Typically, thrombocytopenia can result from 2 causes: a failure of platelet production and/or an increased rate of removal from the blood.

Idiopathic thrombocytopenic purpura (ITP) is a disease where the patient produces antibodies that destroy platelets, which results in thrombocytopenia. ITP is an autoimmune disease that has an incidence rate of 50 to 100 new cases per million per year, with children accounting for half of that number.3

Economics

In clinical trials, initiating the use of white blood cell (granulocyte colony-stimulating factor) 24 hours after myelosuppressive chemotherapy resulted in 50% fewer occurrences of febrile neutropenia and fewer days of intravenous antibiotic usage and hospitalization.4,5 In 1 economic impact study of cancer patients receiving chemotherapy, data were examined from a large US health plan with 10 million covered lives. According to this study, the cost of febrile neutropenia hospitalization was $27,000; the cost for the subsequent febrile neutropeniarelated care was $9900; and the cost for all care related to febrile neutropenia was $37,000. Overall, febrile neutropenia-related charges were more than 10-fold higher among cases than among controls ($40,928 vs $3933).6 The majority of patients with certain tumors who develop neutropenia will either have their chemotherapy postponed or will have their dose decreased, both of which can reduce survival rates.7,8

Demographic/Prevalence Data

  •  The mortality rate associated with febrile neutropenia is 5% to 10%.5
  •  The initial episode of febrile neutropenia is most likely to occur during the first cycle of chemotherapy across all major tumor types.9
  •  Fatigue exists in 14% to 96% of individuals with cancer, particularly in individuals actively undergoing treatment.10
  •  Administration of colony-stimulating factors results in a 50% risk reduction of developing febrile neutropenia.11
  •  The incidence of ITP is approximately 50 to 100 cases per 1 million per year.3
  •  The median diagnosis age of ITP in adults is 56 to 60 years.3
  •  A broad review of clinical trials noted that mild anemia after chemotherapy can occur in 100% of patients and the incidence of more severe anemia can reach 80%.12
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