Erythropoietin and the anemia of cancer.

The pathogenesis of the anemia of cancer involves the combination of a shortened erythrocyte survival in circulation with the failure of bone marrow to increase red cell production in compensation. Inappropriate red cell production is itself related to a conjunction of factors, including impaired availability of reticuloendothelial storage iron, inadequate erythropoietin (Epo) response to anemia, and overproduction of cytokines which are capable of inhibiting erythropoiesis. Many of these cytokines may interfere with erythropoietin production by the kidney. Consequently inadequate serum erythropoietin levels are often encountered in cancer patients, though more frequently in those with solid tumors or multiple myeloma than in those with other hematologic malignancies. There is little evidence supporting a negative impact of chemotherapy, including cisplatin, on erythropoietin production. Rather, chemotherapy usually causes a transient elevation of serum Epo. Red cell transfusions are often administered to cancer patients, possibly resulting, among other deleterious effects, in enhancement of tumor growth. Recombinant human erythropoietin (rHuEpo) has thus been proposed as an alternative. RHuEpo has been shown to be safe and effective in correcting the anemia of cancer and reducing the need for transfusions. The response rate is as good in hematologic malignancies as in solid tumors, but it is extremely poor in those with myelodysplastic syndromes. The effect of rHuEpo does not differ among patients receiving or not receiving chemotherapy, including cisplatin. The probability of response is also similar in patients with adequate or inappropriate erythropoietin production before therapy, although the doses used are usually 2 to 3 times higher than in renal failure patients.