Abstract
Introduction: CD19-CAR-T cells induce high rates of initial response among patients with refractory/relapsed and MRD positive high risk B-cell acute lymphoblastic leukemia (B-ALL). Afterwards allogeneic hematopoietic stem cell transplantation (HSCT) can further reduce relapse rate. Our previous results had shown that CR obtained by CD19 CAR-T had comparable significance to CR by chemotherapy before Allogeneic HSCT in B-ALL.
Patients and Methods: Between July 2015 and Mar 2018, consecutive 135 patients with refractory/relapsed or high risk B-ALL obtained CR with CD19-CART therapy followed by allogeneic HSCT were retrospective analyzed. Median follow-up of survivors was 13 months (range, 3-32 months).
Results: The median age was 11 (2-49) years. The median disease course before transplant was 21(4-143) months. The median time from CART therapy to HSCT was 69 (35-312) days. Disease status was 108 cases relapsed diseases, 11 cases refractory, and 16 persistent/recurrent measurable residual diseases (MRD). MRD pre-conditioning measured by flow cytometry and QT-PCR was positive in 20(14.8%) subjects. Donor source was haploidentical donors in 107(79.3%), identical sibling in 7(5.1%), and unrelated in 21(15.6%). Most subjects (87.4%) received conventional myeloablative pretransplant conditioning with total body radiation (TBI), the rest with busulfan (Bu). Antithymocyte globulin was used in haploidentical and unrelated transplants. Cyclosporine, short-term methotrexate, and mycophenolate mofetil were employed for GVHD prophylaxis. There were no cases of graft-failure except one early death on Day 0 for septic shock. The median time to neutrophil engraftment was 14 days (10, 26 days), and median time to platelet engraftment 14 days (5, 70 days). The incidences of non-relapse mortality within 100 days were 4.4% (0.8, 7.9%) The incidence of grades II-IV acute graft-versus-host disease (GvHD) were 32.1% (24.3, 39.9%) and grades III-IV GvHD 10.5% (5.4, 15.6%). Chronic GvHD and extensive chronic GvHD were 69.7% (60.7, 78.7%) and17.6% (10.7, 24.5%). Cumulative incidence of relapses (CIRs) at 2-year was 11.1% (5.4, 16.8%). There were totally 14 subjects relapsed after HSCT, among which 8 were CD19 negative relapse, 5 CD19 positive and 1 partial CD19 positive. And among the 8 CD19 negative relapse after transplant, 4 subjects had CD19 negative MRD before conditioning. Leukemia-free survival (LFS) was 76.5% (64.2, 88.8%) and overall survival (OS) was 80.8% (72.6, 89.0%) at two years after transplant. In multivariate analysis subjects who were MRD- positive pre-transplant had a higher 2-year CIR (43.5% [18.4, 68.6%] vs. 5.9% [1.2, 10.6%]; p=0.000) and worse 2-year OS (61.5% [35.6, 87.4%] vs. 83.6% [75, 92.2%]; p=0.034).
Conclusions: Our clinical results showed that CART therapy followed by allogeneic HSCT was a promising modality for refractory/relapsed B-ALL. CD19 negative relapse accounted for most relapse after allogeneic HSCT.
No relevant conflicts of interest to declare.
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