Patients

This study was approved by the Institutional Review Board at the Dana-Farber Harvard Cancer Center and conducted under IND 16857 (Holder: E. Hohmann). The study was conducted at the Massachusetts General Hospital Cancer Center. Written informed consent was obtained from all subjects. This trial was registered at ClinicalTrials.gov ({"type":"clinical-trial","attrs":{"text":"NCT02733744","term_id":"NCT02733744"}}NCT02733744). Patients were between the ages of 18 and 75 years and undergoing a first allo-HCT. Eligible conditioning regimens were myeloablative or the combination of fludarabine with melphalan (100-140 mg/m²). Any GVHD prophylaxis regimen was allowed at the discretion of the treating physician. Donors were 8/8 HLA-matched related or unrelated, or haploidentical. Stem cell sources were peripheral blood precursor cells or bone marrow grafts. Patients with a history of inflammatory bowel disease, delayed gastric emptying syndrome, or active gastrointestinal infection were excluded from the trial. In addition, patients who developed acute GI GVHD after HCT and before FMT administration were withdrawn from the trial out of concerns for safety. The decision to use prophylactic antibiotics during the peri-HCT period was at the discretion of the treating physician.