 The study is designed as a phase III, randomized, open label, multicenter, prospective, comparative trial of sirolimus and tacrolimus versus tacrolimus and methotrexate as graft-versus-host disease GVHD prophylaxis after human leukocyte antigen HLA-matched, related, peripheral blood stem cell transplantation in individuals with hematologic cancer. Participants will be stratified by transplant center and will be randomly assigned to the sirolimustacrolimus or tacrolimusmethotrexate arms at a 1:1 ratio. 