Antineoplastic Chemotherapy Induced Anemia: Causes and Treatment
Anemia in Cancer Patients
Anemia is a condition in which red blood cell levels are lower than normal. It is determined by blood hemoglobin levels:
- Normal : greater than 10.9 g/dl
- Mild anemia: 9.5-10.9 g/dl
- Moderate anemia: 8-9.4 g/dl
- Severe anemia: 6.5-7.9 g/dl
- Life-threatening: less than 6.5 g/dl
Cancer induced anemia: Blood cell production (erythropoiesis) is controlled by erythropoietin which responds to low oxygen levels in the blood. In cancer patients the normal erythropoietin response is impaired and red blood cell production is insufficiently stimulated. In addition, tumor cells may infiltrate the bone marrow (the site of blood cell reproduction). Cancer patients may also have anemia due to bleeding or red cell lysis. Other causes of anemia are iron, B12 or folate deficiency. These are absorbed in the gastrointestinal tract, hence patients who have undergone surgical removal of stomach/intestinal tissue are vulnerable to these deficiencies.
Antineoplastic chemotherapy induced anemia: Treatment for malignancy (chemotherapy and radiotherapy) is often myelosuppressive, in that it is toxic to bone marrow cells and hence adversely affects red cell production.
Treatment of Anemia in Cancer Patients
Anemia has many negative effects on patient health. Anemic patients often suffer from fatigue, anxiety and mental impairment. In addition, studies indicate that cancer patients with anemia show significantly poorer survival than those without anemia. One of the reasons for this is that anemia causes low oxygen levels in tumor tissue (hypoxia) which makes the tumor cells less sensitive to chemotherapy and radiotherapy. Hence there is a pressing need to effectively treat antineoplastic chemotherapy induced anemia.
Blood transfusion: Around a third of cancer patients require at least one blood transfusion. Transfusions can provide immediate relief, but this is often short-lived and can carry side effects.
Erythropoiesis-stimulating agents: These growth factors stimulate red cell production. Aranesp is an erythropoiesis-stimulating agent (ESA) approved for the treatment of chemotherapy-induced anemia in non-myeloid malignancies. Early use of ESAs can avoid the need for red cell transfusions and maximize the effectiveness of cancer treatment. However, these agents must be used cautiously since potential side-effects include thromboembolic events such as heart attacks and strokes. The safety of these agents and their beneficial effects on survival have been addressed in recent clinical trials. Prior to ESA treatment, deficiencies in iron, B12 and folic acid must be ruled out. Iron is needed to produce hemoglobin and B12 and folic acid are necessary for the production of red cells. Therefore, patients with deficiencies in any of these are not able to produce red blood cells/hemoglobin sufficiently, regardless of ESA administration.
References
www.cancerconsultants.com: Treatment of Chemotherapy-Induced Anemia by C.Weaver & J.Maxon, 2006.
Erythropoiesis-stimulating agents in patients with cancer: update on safety issues. R.Pinker. Expert Opinion in Drug Safety, 2009, Vol 8, P551-522
