T-Cell Depletion Plus Salvage Immunotherapy With Donor Leukocyte Infusions as a Strategy to Treat Chronic-Phase Chronic Myelogenous Leukemia Patients Undergoing HLA-Identical Sibling Marrow Transplantation

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Abstract
T-cell depletion (TCD) of the donor marrow graft has been shown to reduce the severity of graft-versus-host disease (GVHD) in patients with chronic-phase (CP) chronic myelogenous leukemia (CML) undergoing HLA-identical sibling allogeneic marrow transplantation. However, there has been a corresponding reduction in the graft-versus-leukemia effect so that any decrease in GVHD-related mortality has been offset by an increased rate of disease relapse. Therapy of recurrent disease with donor leukocyte infusions (DLI) has been proven to be effective salvage therapy for the majority of patients who relapse after allogeneic BMT with CP CML. However, the overall impact of salvage DLI therapy on the survival of CP CML patients initially transplanted with TCD marrow grafts is not defined. To address this question, we have evaluated a clinical strategy of TCD followed by targeted adoptive immunotherapy with DLI in 25 CP CML patients undergoing allogeneic BMT from HLA-identical siblings. All patients received a standardized preparative regimen along with ex vivo TCD and posttransplant cyclosporine as GVHD prophylaxis. Durable engraftment was observed in all 25 patients. The incidence of grade II to IV acute GVHD was 8%. The cumulative incidence of transplant-related mortality (TRM) was 4%, and the 1-year probability of overall survival was 96%. The 3-year cumulative relapse incidence was 49%. All relapsed patients received DLI to reinduce remission. The total T-cell dose administered to these patients varied from 0.1 to 5.0 × 108 T cells/kg. Complete responses were observed in 12 of 14 patients, with 1 additional patient still too early to evaluate. Three patients died of GVHD after DLI, and 1 relapsed into blast crisis after a transient cytogenetic remission. Of the remaining 10 patients, 8 are in molecular remission, 1 is alive in relapse, and 1 is receiving DLI treatment. The median follow-up after infusion of surviving DLI patients in remission is 5.3 years. The probability of overall 5-year survival for the entire population is 80%, with a median follow-up of 6.4 years. We conclude that the clinical strategy of TCD followed by targeted adoptive immunotherapy with DLI for those patients with evidence of recurrent disease is a viable transplant strategy for CP CML, resulting in 80% survival and a low risk of acute GVHD and transplant-related mortality.

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