RecruitingPhase 2Drug trialAzacitidine and Chimerism in MDS or AML Patients After Allogeneic Stem Cell TransplantPrevious studies provide a rationale for administration of AZA after allo SCT for decreasing chimerism. The investigators hypothesize that azacitidine can be well tolerated after SCT and help decrease rate of decreasing donor chimerism and hence decrease relapse without increasing GVHD