This is a single institution study of combining decitabine with fludarabine and busulfan in the setting of allogeneic stem cell transplantation. A study population of 20 subjects will be enrolled from The John Theurer Cancer Center at Hackensack University Medical Center. Subjects who are eligible to receive allogeneic hematopoietic stem cell transplantation according to the eligibility criteria will be consented and enrolled. Subjects will receive treatment with decitabine followed by reduced intensity fludarabine and busulfan prior to allogeneic stem cell transplantation. Subjects will be followed until 1 year post transplantation to assess stability of engraftment, toxicity, progression free survival, and disease response