Biological basis of anemia.

Anemia is a frequent complication in cancer, occurring in more than 50% of patients with malignancies. Several factors can cause anemia in these patients, such as blood loss, hemolysis, bone marrow infiltration, hypersplenism, and nutrient deficiencies. However, in a considerable number of patients, no cause other than malignant disease itself can be implicated. This cancer-related anemia is similar to the anemia observed in other chronic diseases, such as rheumatoid arthritis and some chronic infections. The syndrome of anemia of chronic disease is characterized by a hyporegenerative, normocytic, normochromic anemia associated with reduced serum iron and transferrin saturation but elevated (or normal) ferritin levels. Cancer-related anemia results from activation of the immune and inflammatory systems, leading to increased release of tumor necrosis factor, interferon-gamma, and interleukin-1. The cytokine-mediated relative failure of erythropoiesis has been further investigated, and three different mechanisms of action are proposed: (1) impaired iron utilization; (2) suppression of erythroid progenitor cells differentiation; and (3) inadequate erythropoietin production. In addition, the life span of red blood cells is shortened in cancer-related anemia and production cannot compensate sufficiently for the shorter survival time. Administration of recombinant human erythropoietin (r-HuEPO, epoetin alfa) can not only correct inadequate endogenous erythropoietin production, but also can overcome the suppression of erythroid progenitor cells and impairment of iron mobilization.