Disruption of the Oral Microbiota Is Associated With a Higher Risk of Relapse After Allogeneic Hematopoietic Stem Cell Transplantation

Abstract Background: Intestinal microbiota (IM) diversity and composition regulates host immunity and affects outcomes after allogeneic stem cell transplantation (allo-HSCT). Methods: We evaluated how the oral mucosa microbiota (OM) impacts the outcomes in patients who underwent allo-HSCT. Samples from the oral mucosa of 30 patients were collected at three time points: before the conditioning, at aplasia, and at engraftment. We analyzed the associations of OM diversity and composition with allo-HSCT outcomes. Results: Higher OM diversity at preconditioning was associated with a lower risk of relapse in 3 years (33% versus 68%, respectively; P = 0.04). Dominance (relative abundance ≥30%) by a single genus at preconditioning was associated with a higher risk of relapse (63% versus 36%, respectively; P = 0.04), worse progression-free survival (PFS; 19% versus 55%, respectively; P = 0.01), and poorer overall survival (OS) at 3 years (38% versus 81%, respectively; P= 0.02). Conclusion: The presence of Solobacterium at preconditioning was associated with a lower risk of relapse (9% versus 56%, respectively; P = 0.04). This is the first study to address the relationship between OM and clinical outcomes after allo-HSCT.