The purpose of this study is to find out if Darbepoetin alfa is effective in treating low red blood cell levels after allogeneic stem cell transplant. Darbepoetin alfa has been shown to help raise red blood cell levels without blood transfusions.

• Participants will receive Darbepoetin alfa through an injection under the skin, about 28-35 days after their allogeneic stem cell transplant. They will continue to receive the study drug once every three weeks for a maximum of four doses.
• Blood tests will be performed at weeks 3, 6, 9 and 12. The blood tests done at week three will check to make sure the participant has enough iron in their system. If not, they will need to take an iron supplement. Participants will also take a folate supplement to help cell growth and reproduction.

Inclusion Criteria:

• Hematologic malignancies undergoing ablative allogeneic stem cell transplantation for any indication
• 18 years of age or older
• Hgb of less than 10 g/dL at the time of initiation therapy

Exclusion Criteria:

• Known hypersensitivity reaction to darbepoetin alfa or any of its components
• Transfusion of packed red blood cells within 3 days of initiation of treatment with darbepoetin alfa
• Any history of grade III or IV GVHD
• Use of any erythropoietic growth factor since transplantation
• Uncontrolled hypertension
• History of seizure
• Baseline creatinine greater than 2
• Dialysis dependence at the time of enrollment
• Hemolytic uremic syndrome
• Active GI bleeding
• Concurrent autoimmune hemolytic anemia
• Concurrent unstable angina
• History of congenital hypercoagulable state or previous venous or arterial thrombosis
• Relapsed disease prior to the initiation of study treatment
• History of renal cell carcinoma