Donor Lymphocyte Infusion (DLI) post allogeneic stem cell transplant (allo-SCT) in Acute Myeloid Leukemia (AML) and High-Grade Myelodysplastic Syndrome (MDS). A longitudinal retrospective study using peripheral blood (PB) CD34+ and CD3+ donor chimerism (DC) monitoring

Introduction: This longitudinal study was based on the outcomes of Donor Lymphocyte Infusion (DLI) for falling peripheral blood (PB) CD34(+) and CD3(+) donor chimerism (DC). Methods: From 2012 to 2018, data was collected from the BMT database and electronic medical records (EMR). The primary objective was to compare the indication for DLI based on falling PB CD34(+) or CD3(+) DC in patients post allo-SCT for AML and MDS and their overall survival (OS). Results: 18/70 patients met the inclusion criteria. Indications for DLI were i) falling PB CD34(+) DC <= 80 % with morphological relapse, ii) falling PB CD34(+) DC <= 80 % without morphological relapse and iii) falling PB CD3(+) DC <= 80 % without falling PB CD34(+) DC. Log rank analysis showed falling PB CD34(+) DC and morphological relapse had significantly lower OS. Linear regression demonstrated better OS post DLI if there was PB CD34(+) and CD3(+) chimerism response at 30 days (p = 0.029), GVHD (p = 0.032) and tapering immunosuppression at the time of falling DC (p = 0.042). Conclusion: DLI for PB CD34(+) DC values <= 80 % and morphological relapse had the lowest OS. In this study, full DC was achieved after DLI even with a PB CD3(+)DC value as low as 13 %, provided the PB CD34(+) DC remained > 80 %. Further research is vital in CD34(+) DC as a biomarker for disease relapse and loss of engraftment.