Hemopoietic Reserve in the Older Cancer Patient: Clinical and Economic Considerations

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Abstract
Older individuals are at increased risk for myelosuppression, the most common complication of cytotoxic chemotherapy. Causes include reduction in hemopoietic stem cell reserve, increased prevalence of chronic diseases, and increased prevalence of anemia. Anemia is an independent risk factor for myelotoxicity, in part because it decreases the volume of distribution of anthracyclines, epipodophyllotoxins, and taxanes and increases the circulating concentration of free drugs. The authors review the effects of aging on the hemopoietic system and the consequences of reduced hemopoietic reserve on the safety and cost of chemotherapy. While it is unclear whether the responsiveness of hemopoietic progenitors to physiologic amounts of growth factors is preserved in older individuals, pharmacological doses of these factors stimulate hemopoiesis and mitigate myelosuppression. It is recommended that patients aged 70 and older receiving combination chemotherapy of dose-intensity comparable to CHOP be routinely treated with myelopoietic growth factor. The hemoglobin levels of these patients should be maintained at approximately 12 g/dL with erythropoietin. This treatment may prevent costly complications such as neutropenic infections and functional dependence. Alternative approaches to the prevention of hemopoietic complications may include more conservative use of growth factors (later initiation of treatment and earlier termination), prophylactic antibiotics in patients at risk for prolonged neutropenia, and biological treatment. Dose-reduction of chemotherapy may lead to inferior outcomes and is not recommended for patients with good functional status.