Abstract 598: Utility of cell therapy to control relapsed acute myeloid leukemia following allogeneic stem cell transplantation: Does cell source matter
Authors: Park Woochan , Kim Inho , Yoon Sung-soo , Park Seonyang , Koh Youngil 
Published: August 2018

Abstract
Introduction: Although allogenic hematopoietic stem cell transplantation (Allo-SCT) is curative therapy for acute myeloid leukemia (AML), many patients experience relapse following allo-SCT. For these patients, it is well known that donor lymphocyte infusion (DLI) could rescue a certain proportion via graft versus leukemia effect. On the other hand, with the advance of abundant stem cell harvesting techniques, residual stem cell after allo-SCT is also frequently used as a rescue therapy for AML relapse. However, clinical utility of residual stem cell is not well established yet. Hence, in this study, we compare the outcome of DLI with residual stem cell infusion in relapsed AML after allo-SCT.
Materials and Methods: We retrospectively reviewed the AML patients who underwent DLI or residual stem cell infusion for relapsed disease after allo-SCT from 2001 to 2017 in Seoul National University Hospital. We analyzed factors including overall survival (OS), cell counts, disease status at cell therapy, and GVHD development. Our primary outcome was to compare OS after cell therapy between DLI group and residual stem cell group.
Results: A total of 81 patients were analyzed. There were 50 patients (25 males and 25 females) who received cell therapy using DLI, and 31 patients (11 males and 20 females) who received residual stem cell infusion. There was no difference in age and duration from allo-SCT to cell therapy between the two groups. Majority of patients received cell therapy for first relapse after allo-SCT (63% in DLI, 93% in residual stem cell group). Median CD3 cell count infused was not different between DLI and residual stem cell product (median value of 0.967 X 108/kg and 0.964 X 108/kg). Median CD34 cell dose was 2.34 X 106/kg in residual stem cell group.
There was no difference in OS between the two groups (median OS 8.5 months for DLI and 10.2 months for residual stem cell group, p-value 0.673). GVHD occurred in 44% in DLI group and 41.9% in residual stem cell group. When multivariate analysis was performed, disease status at stem cell therapy or duration from allo-SCT to relapse did not show any significant difference. Characteristics of long-term survivors after cell therapy following relapse after allo-SCT could be summarized as whether to acquire bone marrow CR after therapy.
Conclusion: This study demonstrates that clinical utility of DLI and residual stem cell infusion is similar in relapsed AML after allo-SCT. Hence, residual stem cell could be used as an alternative source for T-cell therapy following allo-SCT.
Citation Format: Woochan Park, Inho Kim, Sung-soo Yoon, Seonyang Park, Youngil Koh. Utility of cell therapy to control relapsed acute myeloid leukemia following allogeneic stem cell transplantation: Does cell source matter [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 598.