Abstract
BACKGROUND: Microchimerism dynamics following allogeneic hematopoietic stem cell transplantation (allo-HSCT) may predict engraftment and clinical outcomes. This study aimed to quantify microchimerism changes and assess their clinical significance. METHODS: In this retrospective study, eighteen patients undergoing allo-HSCT received either an enhanced dual-conditioning (EDCT) regimen (fludarabine/busulfan/cytarabine plus cyclophosphamide 200 mg/kg) or a modified EDCT regimen. Microchimerism levels were serially monitored from day +1 post-transplantation. RESULTS: Complete donor chimerism (CDC) was achieved in 16/18 patients (88.9%) at a median time of 14 days (range, 9-24). The median neutrophil and platelet engraftment times were 15 days (range, 11-28) and 25 days (range, 10-80 in 16 patients who had platelet engraftment), respectively. Among them, eight patients retained constant CDC, 3 developed one increasing mixed chimerism (IMC), while 5 had multiple IMCs. Patients with constant CDC demonstrated faster platelet engraftment (median, 19.5 vs. 40 days, P = 0.066) and superior overall survival (OS, median, not reached vs. 5.0 months, 95% CI 2-10 months, P = 0.015). Notably, microchimerism trends differed between peripheral blood stem cell transplantation (PBSCT) and cord blood transplantation (CBT) recipients. The PBSCT group exhibited shorter neutrophil (median: 14.5 vs. 17.5 days, P = 0.165) and platelet (median: 15 days vs. 40 days, P = 0.009) engraftment times compared to the CBT group. However, the final CDC rates and OS times did not differ significantly between the two groups. CONCLUSION: Early microchimerism dynamics correlate with engraftment efficiency and survival outcomes in allo-HSCT patients, suggesting its clinical utility for timely intervention and personalized treatment adjustment. The promising long-term outcomes support the applicability of this regimen and monitoring approach across transplantation modalities.