Abstract:

Objective: The level of donor-recipient chimerism is an established method to document donor engraftment. Allogeneic stem cell transplantation(ASCT) may result in mixed hematopoietic chimerism (MC), especially after reduced intensity conditioning regimens. Increasing MC levels in the post ASCT period may indicate disease relapse, graft failure, or rejection. In this study we aimed to study clinical outcome of mixed chimerism after ASCT in patients with hematological diseases. Methods: The data of 335 patients whose ASCT were performed at our center between 2009 and 2019 and survived more than three months after transplantation were analyzed retrospectively. Results: During follow up period 127 (43%) of 293 patients in full chimeric (FC) group and 11 (26.1%) of 42 patients in MC group died.  11 patients received donor lymphocyte infusions (DLI) after MC detected, 4 of them converted into FC. 10 mix chimeric patients converted into FC spontaneously. In 3 patients no donor cell was observed in time (0%). 2 of them are still in remission. 25 patients remained mix chimeric during follow up period. 66 patients received reduced intensity conditioning (RIC) regimen and 10 (15.1%) of them had MC during follow up period. 269 patients received myeloablative conditioning (MAC)  regimen and 32 (11.8%) of them had MC during follow up period. Conclusion: ASCT may result in MC especially after RIC regimens. MC does not always related with relapse risk and mix chimeric patients with malignant or benign hematological diseases can stay in remission for a long time. 

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