T-Cell Depletion in Allogeneic Hematopoietic Cell Transplantation for Chronic Lymphocytic Leukemia: A Retrospective EBMT Analysis.
Authors: Schetelig Johannes , Milligan Donald , Niederwieser Dietger , Volin Liisa , Maertens J. , Gratwohl Alois , Bornhaeuser Martin , Van Gelder Michel , Brand Ronald , de Witte T. M. , Dreger Peter 
Published: October 2019

Abstract
Abstract 2307
Poster Board II-284

Objectives:
T-cell depletion (TCD) is controversial in patients with chronic lymphocytic leukemia (CLL). While TCD is a powerful tool to prevent graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT) concern is raised about an increased incidence of relapse. The aim of this retrospective analysis was to study the impact of in vivo TCD in patients with CLL registered with the EBMT database.

Patients and Methods:
Patients with CLL who received allogeneic HCT from a matched sibling (SIB) or unrelated donor (UD) and cyclosporine-based GVHD prophylaxis between 2001 and 2008 were eligible. Patients who received ex vivo T-cell depleted grafts were excluded. The outcome of three major groups of patients was compared: Patients who were transplanted without TCD, those who received anti-thymocyte globulin (ATG) and patients who received alemtuzumab (CAM). Baseline and follow-up data were downloaded from the EBMT database.

Results:
413 patients were eligible. 73% of patients had SIB donors and 27% matched UD. Reduced intensity conditioning regimens were applied for the majority of patients (82%). No TCD was used in 234 patients, while 100 patients received CAM and 79 patients ATG. The median follow-up after HCT was 22 months (1 to 92 months).
Univariate comparisons of GVHD and the rates of DLI are reported for patients with matched sibling donors only. After SIB-HCT the cumulative incidence of acute GVHD II-IV was 7% with CAM, 22% with ATG and 34% without TCD (gray test, p=0.0001). Subsequently, 28% of patients with CAM received prophylactic donor lymphocyte infusions (DLI) compared to 5% of patients with ATG and 9% without TCD (p=0.03). DLI for any reason was given to 45% of patients with CAM, 24% with ATG and 15% without TCD (p=0.009). As a result of late-onset GVHD the incidence of chronic GVHD after TCD with CAM increased from 20% at 1 year to 60% at 4 years after SIB-HCT. At 4 years after HCT comparable cumulative incidences of chronic GVHD were observed (70% without TCD, 59% after ATG and 60% after CAM; p=0.1).
For the whole cohort of patients 4-year overall survival (OS) and progression-free survival (PFS) were 57% (95% CI, 50% to 64%) and 44% (95% CI, 37% to 51%). At 4 years the cumulative incidence of relapse was 28% (95% CI, 17% to 39%) and the incidence of non-relapse mortality was 28% (95% CI 18% to 38%). In multivariate Cox regression analysis of PFS when GVHD prophylaxis without TCD was used as reference category the adjusted hazard ratio for TCD with CAM was 1.4 (95% CI, 0.9 to 2.2, p=0.2) and for TCD with ATG 1.4 (95% CI, 0.9 to 2.3, p=0.1). For relapse incidence the adjusted hazard ratio for TCD with CAM was 1.4 (95% CI, 0.7 to 2.6, p=0.3) and for TCD with ATG 1.0 (95% CI, 0.5 to 2.1, p=0.9) and for non-relapse mortality the adjusted hazard ratio for TCD with CAM was 1.4 (95% CI, 0.8 to 2.8, p=0.3) and for TCD with ATG 1.9 (95% CI, 1.0 to 3.5, p=0.06).

Conclusion:
In patients with CLL the combination of in vivo TCD and DLI appears to result in comparable rates of chronic GVHD and PFS compared to T-cell replete HCT.

Disclosures:
Schetelig: Bayer Schering: Research Funding.