Clinical impact of early microchimerism dynamics after transplantation with enhanced dual-conditioning regimen in...

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.

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.

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.

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.