Microbiota changes during allogeneic hematopoietic stem cell transplantation has several known causes: conditioning chemotherapy and radiation, broad-spectrum antibiotic administration, modification in nutrition status and diet, and graft-versus-host disease. This article aims to review the current knowledge about the close link between microbiota and allogeneic stem cell transplantation setting. The PubMed search engine was used to perform this review. We analyzed data on microbiota dysbiosis related to the above-mentioned affecting factors. We also looked at treatments aimed at modifying gut dysbiosis and applications of fecal microbiota transplantation in the allogeneic stem cell transplant field, with particular interest in fecal microbiota transplantation for graft-versus-host disease (GvHD), multidrug-resistant and clostridium difficile infections, and microbiota restoration after chemotherapy and antibiotic therapy.

Introduction: Autologous stem cell transplantation (ASCT) is regaining interest as a consolidation strategy for acute myeloid leukemia (AML) patients with favorable/intermediate risk and measurable residual disease (MRD) negativity. In fit older adults, its role remains debated due to concerns regarding toxicity and stem cell collection. Aim: To evaluate the long-term outcomes of ASCT in AML patients aged ≥60 years in first complete remission (CR1). Methods: We retrospectively analyzed 43 non-M3 AML patients (median age 64, range 60–72) who underwent ASCT in CR1 across five centers (2000–2024). Risk was stratified by ELN 2017. Primary endpoints were overall survival (OS) and disease-free survival (DFS). Results: The cohort included 22 favorable-risk and 21 intermediate-risk patients. Most (88%) achieved CR1 after one induction course. Median neutrophil and platelet engraftment occurred at 13 and 15 days, respectively. Grade III/IV infections were observed in 28% of patients; transplant-related mortality was low at 4%. At a median follow-up of 77 months, 5-year OS and DFS were 51% (95% CI: 37–70%) and 47% (95% CI: 34–65%), respectively. OS was significantly superior in favorable- versus intermediate-risk patients (68% vs. 35%, p = 0.027), with a similar trend for DFS (57% vs. 35%, p = 0.07). The number of consolidation cycles did not impact survival outcomes. Conclusions: This multicenter study confirms that ASCT is a feasible and effective consolidation strategy for selected fit AML patients aged ≥60. The low mortality and encouraging survival, particularly in favorable-risk subgroups, support ASCT as a valid alternative to prolonged chemotherapy or maintenance.