TAC/MTX vs. TAC/MMF/PTCY for Prevention of Graft-versus-Host Disease and Microbiome and Immune Reconstitution Study (BMT CTN 1703/1801)

1703: Graft-versus-Host Disease (GVHD) is a complication that affects many hematopoietic stem cell transplant (HSCT) patients; it occurs when the new cells from a transplant attack the recipient's body. The current standard GVHD prophylaxis regimen for patients with hematologic malignancies undergoing HSCT involves a combination of immunosuppressive agents given for the first 6 months after transplant. The standard strategy of Tacrolimus/Methotrexate will be used as a control arm in comparison to one other treatment plan utilizing Tacrolimus/Mycophenolate Mofetil/Post-Transplant Cyclophosphamide. Study participants will receive an infusion of mobilized peripheral blood stem cell grafts on both arms. Study participants will be randomized to one of these two treatment arms. 1801: A relationship between the intestinal microbiota and graft-versus-host disease (GVHD) has long been appreciated but is still not well understood. Mice transplanted in germ-free conditions or treated with gut-decontaminating antibiotics developed less severe GVHD. Clinical studies initially suggested a benefit from near-total bacterial decontamination, but later showed no clear benefit and this approach was discontinued in the early 1990s. Partial gut decontamination continues to be practiced at many centers. More recently, the advent of next-generation sequencing (NGS) has resulted in cheaper and easier characterization of complex microbial mixtures. This has led to a renewed interest in evaluating the relationship between the microbiota and human health and disease, including recipients of hematopoietic cell transplantation (HCT). Similarly, NGS has also contributed to significant advancements in the investigator's understanding of immune reconstitution in HCT patients and how this may impact clinica outcomes. The goal of this protocol is to test the primary hypothesis that the engraftment stool microbiome diversity predicts one-year non-relapse mortality in patients undergoing reduced intensity allogeneic HCT.