Prediction of response to treatment with recombinant human erythropoietin in anaemia associated with cancer.

The anaemia associated with cancer can be effectively treated with recombinant human erythropoietin (rHuEpo) in about 60% of the patients. However, the response rate varies according to treatment modalities as well as the response criteria used. A number of disease- or chemotherapy-related factors determines the probability of response. Several specific mechanisms of anaemia, such as haemolysis, splenomegaly, bleeding, haemodilution, or ineffective erythropoiesis can seriously interfere with response. However, the type of tumor, in particular haematologic versus non-haematologic, is not critical, except in situations of major marrow involvement and limited residual haematopoiesis. Stem cell damage by previous therapy, reflected by low platelet counts or high transfusion needs, will impair response. In addition, marrow suppression by current intensive chemotherapy will also have a negative impact. Besides its intensity, the type of chemotherapy may not be critical, although patients undergoing platinum-based chemotherapy may respond faster than those receiving non-platinum regimens. Complications such as infections, bleeding or nutritional deficiencies may have a major negative impact on outcome. An important response-limiting factor is functional iron deficiency, i.e. an imbalance between iron needs in the erythropoietic marrow and iron supply, which depends on the level of iron stores and its rate of mobilisation. Therefore, oral or preferably intravenous iron supplements should be given when serum ferritin is below 40-100 micrograms/l, reflecting the absence of iron stores, or when the percentage of hypochromic red cells rises above 10%, indicating functional iron deficiency even in the presence of adequate storage iron. Because up to 40% of the patients will not respond to rHuEpo, it is of utmost importance to develop models that could help predict response to rHuEpo and thus select the most appropriate cancer patients for this therapy. Most studies of patients with myeloma or lymphoma have indicated that patients with a low baseline serum Epo level will respond better, but this is not true of patients with solid tumors. Also of considerable interest are early changes of erythropoietic parameters after 2 to 4 weeks of treatment, including increments of serum transferrin receptor (sTfR), reticulocytes and haemoglobin, as well as the persistence of elevated ferritin or Epo levels. Combination of baseline serum Epo and the 2-week increment of sTfR or haemoglobin may provide the best prediction of response.