Bendamustine With or Without Cyclophosphamide in Preventing GVHD in Patients Undergoing Stem Cell Transplant

Inclusion Criteria: * Patient with hematologic malignancies. * Donor: Matched sibling, matched unrelated, mismatched or haploidentical * Zubrod performance 0 to 2 or Karnofsky of at least 60. * Adequate organ function at time of study entry: 1. Creatinine less than or equal to 1.6 mg/dL and creatinine clearance \>/= 30 ml/min. Creatinine clearance will be calculated using the Cockcroft-Gault equation 2. Total bilirubin less than \< 1.5 x UNL 3. SGPT \< 2.5 x ULN 4. Ejection fraction \>/= 40% 5. FEV1, FVC and DLCO \>/= 40% * Female patients of childbearing potential must agree to use an effective method of birth control while on study and for 6 months after the last dose of bendamustine. Male patients with female partners of childbearing potential must agree to use an effective method of birth control while on study and for 3 months after the last dose of bendamustine. Exclusion Criteria: * Pregnant or nursing women. * Known to be HIV positive * Active and uncontrolled disease/infection * Unable or unwilling to sign consent * Current active hepatic or biliary disease (with exception of Gilbert's syndrome) * Active hepatitis B or C. * Toxicities (grade \> 1) unresolved from prior treatment (including chemotherapy, targeted therapy, immunotherapy, experimental agents radiation, or surgery. * Patients with standard risk acute leukemia in first complete remission and patients with chronic myeloid leukemia in first chronic will be excluded during escalated phase.