RecruitingPhase 1Drug trialPost-Transplant Cyclophosphamide in Patients Aged >/= 65 Years Undergoing Haploidentical TransplantThe purpose of this phase 1 study is to determine the optimal dose of the immune suppressive drug, cyclophosphamide, following standard allogeneic stem cell transplant in patients aged \>/= 65 years with hematologic malignancies.