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Alloreactivity triggered by interaction between killer cell immunoglobulin-like receptors ( KIRs) and natural killer ( NK) cells plays a role in the graft-versus-tumor effect after hematopoietic stem cell transplantation ( SCT). Our aim in this study was to evaluate this role in the setting of T-cell-repleted haploidentical SCT with postinfusion high-dose cyclophosphamide ( PT-Cy). We included 33 patients. Among patient-donor pairs with at least 1 inhibitory KIR ( iKIR) gene mismatch, event-free survival ( EFS) and cumulative incidence of relapse 1 year after transplant were significantly better (85% vs. 37% [ P = 0.008] and 18% vs. 46% [ P = 0.041], respectively). A subanalysis in 12 patients with Hodgkin's lymphoma ( HL) showed an improvement in EFS 1 year after transplant in those patients with KIR ligand mismatch (100% vs. 25%, P = 0.012), although overall survival ( OS) was not affected (85% vs. 80%, P = 0.2). Eight of 12 patient-donors pairs presented iKIR mismatches. Of note, this outcome was better in the small subgroup, both for EFS (100% vs. 25%, P = 0.012) and for OS (100% vs. 37%, P = 0.004). Our data suggest that in the setting of T-cell-repleted haploidentical SCT with PT-Cy, iKIR mismatch is associated with improved survival, with particularly good results for both iKIR and KIR ligand mismatches in patients with HL. [ABSTRACT FROM AUTHOR]

Allogeneic stem cell transplantation (allo- SCT) has become the treatment of choice in patients with intermediate-risk and high-risk acute myeloid leukemia ( AML). The quality of response to treatment, assessed in terms of detection of minimal residual disease ( MRD), has been consistently associated with prognosis and clinical outcome in patients with AML. The aim of the present study was to evaluate the prognostic impact of analyzing MRD in bone marrow using 4-color multiparametric flow cytometry ( MFC) in 29 patients with AML before and after allo- SCT. Eighteen patients who were shown to be MRD-negative [≤0.1% leukemia-associated immunophenotypes ( LAIPs)] by MFC at transplantation and underwent allo- SCT had lower rates of relapse (15% vs. 66%, P = 0.045), better overall 1-yr survival (83% vs. 52%, P = 0.021) and a lower cumulative incidence of relapse ( P = 0.032) than patients who were MRD-positive (>0.1%). All post-transplant MRD-positive patients underwent a therapeutic intervention after transplant (tapering of immunosuppression, donor lymphocyte infusion, or re-transplant) with the intention of preventing relapse. Disease was controlled and MRD disappeared in five of these patients. Disease recurred in the other seven patients. We can conclude that follow-up with MFC for the detection of MRD in AML before and after SCT is useful for predicting relapse. In the post-transplant setting, monitoring of MRD by MFC could be a key preemptive intervention. [ABSTRACT FROM AUTHOR]