rHuEPO and treatment outcomes: the preclinical experience

The presence of hypoxic areas is a common feature of solid tumors and has been associated with decreased sensitivity of the tumors to radiation therapy and oxygen-dependent chemotherapeutic agents, as well as worsened outcomes, including survival. Anemia is also common in cancer patients and is believed to contribute to tumor hypoxia. Thus, the rationale exists for administering recombinant human erythropoietin (rHuEPO, epoetin alfa) in an effort to increase hemoglobin levels, correct anemia, and thereby possibly increase the sensitivity of tumors to standard cancer treatment and improve patient outcomes. The results of several preclinical studies that examined the impact of anemia prevention by rHuEPO on tumor sensitivity to radiation therapy in rodent models of cancer showed that induction of anemia increased hypoxia in tumor cells and that correction of anemia with rHuEPO could improve tumor oxygenation. Further studies in rodent models showed significantly delayed tumor growth in both irradiated mice and irradiated rats treated with rHuEPO. In those studies, the increased radiosensitivity observed was believed to be due to improved tumor oxygenation following the correction of anemia. Similarly, enhancements in chemosensitivity were found in rHuEPO-treated rodent models. In the chemosensitivity studies, as in the radiosensitivity studies, the therapeutic benefit obtained was believed to reflect improved tumor oxygenation subsequent to an rHuEPO-related increase in oxygen availability. One study evaluated the potential biologic effects of epoetin alfa on tumor progression using murine myeloma models (MOPC-315 and 5T33 MM). Treatment of MOPC-315 tumor-bearing mice with epoetin alfa induced complete tumor regression in 30%-60% of mice. Regression was found to be tumor specific, and the effect of epoetin alfa was shown to be T-cell mediated. Additionally, epoetin alfa administration prolonged survival and reduced morbidity and mortality in the 5T33 MM tumor model. Those investigators suggested that epoetin alfa may have antitumor activity in addition to its hematopoietic effects. Overall, these preclinical findings suggest that correction of anemia by rHuEPO can increase tumor sensitivity to both radiation therapy and chemotherapy and that epoetin alfa may exert an immunomodulatory effect in multiple myeloma.