Chronic disease and cancer chemotherapy

Anaemia often becomes a characteristic feature of several chronic diseases, such as rheumatoid arthritis. In most instances this can be linked to lower than normal endogenous serum EPO levels (although in some cases a deficiency of iron or folic acid can also represent a contributory factor). Several small clinical trials have confirmed that administration of EPO increases haematocrit and serum haemoglobin levels in patients suffering from rheumatoid arthritis. A satisfactory response in some patients, however, required a high-dose therapy that could render this therapeutic approach unattractive from a cost benefit perspective. 

Severe, and in particular chronic, infection can also sometimes induce anaemia, which is often made worse by drugs used to combat the infection. For example, anaemia is evident in 8 per cent of patients with asymptomatic HIV infection. This incidence increases to 20 per cent for those with AIDS-related complex, and is greater than 60 per cent for patients who have developed Kaposi s sarcoma. Up to a third of AIDS patients treated with zidovudine also develop anaemia. Again, several trials have confirmed that EPO treatment of AIDS sufferers (be they receiving zidovudine or not) can increase haematocrit values and decrease transfusion requirements. 

Various malignancies can also induce an anaemic state. This is often associated with decreased serum EPO levels, although iron deficiency, blood loss or tumour infiltration of the bone marrow can be complicating factors. In addition, chemotherapeutic agents administered to this patient group often adversely affect stem cell populations, thus rendering the anaemia even more severe. 

On a more cautionary note, the EPO receptor is expressed not only by specific erythrocyte precursor cells, but also by endothelial, neural, and myeloma cells. Concern has been expressed that EPO, therefore, might actually stimulate growth of some tumour types, particularly those derived from such cells. To date, no evidence (in vitro or in vivo) has been obtained to support this hypothesis. 

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