Impact of Antithymocyte Globulin-Containing Conditioning Regimens on Patients Undergoing Allogeneic Stem Cell Transplantation for Progressive Myelodysplastic Syndrome: A Report From the SFGM-TC Group
Authors: Yakoub-Agha Ibrahim , Damaj Gandhi , Robin Marie , Vigouroux Stephane , Garnier Alice , Michallet Mauricette , El-Cheikh Jean , Lioure Bruno , Simon Audrey , Bay Jacques-Olivier , Bordigoni Pierre , Contentin Nathalie , Maillard Natacha , Deconinck Eric , Lapusan Simona , Guillerm Gaelle , Legrand Faezeh , Marry Evelyne , Mohty Mohamad , Duhamel Alain 
Published: October 2019

Abstract
Abstract 3035

Background:
due to a risk of relapse of underlying disease in patients transplanted with progressive malignancy, the use of antithymocyte globulins (ATG), incorporated within the conditioning regimen prior to allogeneic stem cell transplantation (allo-SCT), is still controversial. We report here on a study of 245 consecutive patients transplanted between January 1999 and December 2009 in 26 French and Belgian centers for progressive MDS, defined as stable, untreated, relapsed or refractory disease.

Patients and Methods:
Inclusion criteria included patients aged over 18 who received allo-SCT from either a sibling (n=153) or HLA-A, -B, -C, -DRB1 and -DQB1 allele matched unrelated donor (10/10) (n=86) for MDS or AML/RAEB-t (with 20–30% BM blasts). Data quality was ensured using computerized discrepancy errors and vigorous on-site data verification of every single file. A qualified research technicien has been appointed by the University-Hospital of Lille to assist on-site centers that couldn't meet data quality requirements. HLA matching was double-checked by the French Bone Marrow Donor Registry.

Results:
The first 239 files analyzed until now are presented, including 154 males and 85 females. According to the WHO classification at diagnosis, 85 patients had RA/RARS/RCMD, 86 RAEB1, 62 REAB2 and 6 RAEB-t/AML. Sixty-six patients had progressed to a more advanced disease before allo-SCT. At diagnosis, 102 patients had an IPSS int-2 or higher. Cytogenetic IPSS was recorded as favorable (n=109), intermediate (n=61), unfavorable (n=63) and missing (n=6). Disease status at transplant was established as follows: relapsed or refractory disease (n=106) and untreated or stable disease without hematological improvement (n=133). Median age at transplantation was 53 years (range, 20–70). Patients received myeloablative conditioning (n=105) and nonmyeloablative (n=134) including busulfan-based regimens (n=127), TBI-based regimens (n=92) or other alkylating-agent-based regimens (n=20). In this series, 95 patients (40%) received ATG as part of conditioning ('ATG' group), whereas 144 did not ('no-ATG' group). The analysis reference date of April 1st 2011, median follow-up in survivors was 50 months (IQR, 33–92) with 59 patients having died of relapse and 77 of TRM. The estimated 3-year OS and EFS was respectively 42.3%, and 32.4%. The probability of relapse, overall and event-free survival at 3 years was not significantly different between the two groups. In contrast, the cumulative incidence of grade 2–4 acute GVHD was 48% in the no-ATG group and 30% ATG group (P <.001) and the cumulative incidence of grade 3–4 acute GVHD was 24% and 11% respectively (P <.001). Although the cumulative incidence of chronic GVHD was similar in the no-ATG and ATG groups (64% vs 46%, p=.15), a trend for a lower TRM was observed in the ATG group (22% vs 31%, p=.06). In multivariate analysis, the absence of use of ATG was the strongest parameter associated with an increased risk of acute grade 2–4 [HR = 2.28, 95% CI: 1.39–3.74, p=.001] and grade 3–4 GVHD [HR = 2.19, 95% CI: 1.04–4.61, p=.035].

In conclusion,
the addition of ATG to the conditioning regimen resulted in a decreased incidence of acute GVHD without increasing relapse rates and compromising patient survival undergoing allo-SCT for progressive MDS.

Disclosures:
Yakoub-Agha: Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Research Funding; Fresinus: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria. Michallet:Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees; Fresinus: Honoraria, Membership on an entity's Board of Directors or advisory committees. Deconinck:Celgene: Honoraria. Mohty:Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees.