Anemias are conditions in which the numbers of red blood cells or the amount of hemoglobin in them is below normal. 3Hematopoiesis is the normal process of blood cell development, and is dependent of the smooth functioning of three factors: (1) the continuing presence of stem cells that are capable of differentiating and developing in to mature blood cells, (2) a bone marrow environment that is supportive of stem cell survival and functioning, and (3) a complex system of highly regulated hematopoietic growth factors that regulate the proliferation, differentiation, and survival of blood cells. Anemia results when this system fails to function properly.
Anemia can be a very debilitating condition affecting virtually every organ and tissue of the body. A primary symptom of anemia is fatigue, greatly affecting the quality of the patient’s life. The occurrence of anemia can be the first diagnostic clue to suggest a malignant disease, and is present in more than 30% of cancer patients. It is very important to recognize and treat anemia, as it strengthens the patient to combat the cancer. The presence of anemia in cancer patients increases the overall relative risk of death by 65%. 1
Anemia due to direct effects of the cancer 5
Some cancers cause anemia due to blood loss. Cancers that affect the gastrointestinal and genitourinary tracts, for example, can cause bleeding of the surrounding tissues. Large, bulky tumors such as hepatoma and ovarian cancer can bleed from within the tumors.
Normally, red blood cells have a life span of around 120 days. Scavenger cells known as histiocytes or macrophages in the bone marrow, liver or spleen detect and destroy these spent cells by engulfment. Some cancers lead to an excessive destruction of red blood cells by this process.
Certain cancers such as leukemias, lymphomas, myelomas and breast and prostate carcinomas invade the bone marrow. They can compromise bone marrow functioning by physical displacement of marrow content by the tumor, or by changes in the marrow such as the formation of abnormal amyloid protein, necrosis (dead tissue), and fibrosis.
Cancers that do not invade the bone marrow can cause the “anemia of chronic disease.” 5 This term implies that the causative mechanism is incompletely defined, but appears to be due to an inflammatory response of the body to the cancer. This immune response results in the secretion of proteins called cytokines that serve a signaling function between components of the immune system. These cytokines appear to reduce the production of some hematopoietic growth factors, notably erythropoietin, and can impair the bone marrow response to erythropoietin.
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