Observational Study of the Combination of Post-transplant High Dose Cyclophosphamide, Tacrolimus and Mycophenolate Mofetil for the Prevention of Acute Graft-versus-Host Disease in Patients Eligible to Allogeneic Hematopoietic Stem Cell Transplant

Inclusion Criteria:

1. Patient is scheduled for transplant of 'mobilized' peripheral blood stem cells (PBSC) from a genotypically HLA-unrelated or related identical or partially mismatched stem cell donor.
2. Patient is ≥ 18 years and ≤ 65 years of age.
3. Diagnosis of malignancy. Patients will be divided on the basis of their disease in low risk and high risk patients.

   High risk diseases: AML \> CR1, ALL \> CR1, CML in CP #2, AP or BP, non-Hodgkin's lymphoma \> CR2, Hodgkin's lymphoma \> CR2, other patient with refractory malignancy Low risk: multiple myeloma (all patients), AML in CR1, myelodysplastic syndrome beyond RA (including CMML) and ALL in CR1.
4. Patient or legal guardian has signed/dated the informed consent form.
5. Female patients must have a negative pregnancy test (blood or urine) unless they are prepuberal or surgically sterile.
6. Estimated Creatinine Clearance ≥ 60 mL/min at time of consent.
7. Total bilirubin is ≤ 1.5 times the upper limit of normal at time of consent.
8. SGOT and SGPT are ≤ 2.0 times the upper limit of normal at time of consent.

Exclusion Criteria:

1. Patient \> 65 years of age
2. Patient has not signed/dated the informed consent form.
3. Patient is receiving a T-cell depleted hematopoietic stem cell graft.
4. Pregnant or lactating women
5. Patient has an acute pulmonary infection suspected on the basis of abnormal chest x-ray.
6. Patient has an active systemic infection not controlled with anti-microbial therapy.
7. Patient is a known carrier of any of the Human Immune Deficiency Viruses (HIV-1 or others).