Is Antilymphocyte Globulin Useful in Conditioning Regimen of Unrelated Donor Hematopoïetic Stem Cell Transplantation?.

Between 1998 and 2004, 2141 allogeneic hematopoietic stem cell transplantations with unrelated donor (excluding cord blood) have been recorded on the SFGM-TC data base. The lack of unique behavior in regard of Anti Lymphocyte Globulin (ALG) use in unrelated donor transplants allowed us to perform a retrospective study to assess the influence of ALG in such grafts. To avoid biaises we excluded T cell depletion or monoclonal antibody use, reduced intensity conditioning and focused only on patients (pts) with acute leukemia (AL) and myelodysplasia (MDS). So we defined a study population of 553 pts. In addition, in order to analyze the actual impact of ALG on wellknown targets (engraftment, acute GvHD, relapse, survival) we choose to keep only the cases in which was available the allelic HLA typing (4 digits) for the recipient and the donor, i.e. 250 pts. There were 106 females and 144 males, allografted in 29 centers. The median age was 23 years (1–62) and there were 77 children under 15. There were 223 AL - myeloid n=120, lymphoid n=103 - and 27 MDS. The source of cells was bone marrow for 190 pts and peripheral mobilized stem cells for 60. One hundred and ninety-three pts received a conditioning regimen including Total Body Irradiation. Ninety-five pts received ALG (mainly Thymoglobulin Mérieux-Genzyme Lyon France at various doses) for a median of 3 days (group 1) and 155 did not (group 2). There were 189 donor/recipient pairs strictly HLA-matched 10/10, 49 with one allelic difference (HLA A n=13; HLA B n=8; HLA C n=13; HLA DRB1 n= 5; HLA DQB1 n=10 ), 11 with 2 allelic differences and 1 with 3 allelic differences. 238 pts have sustained engraftment at a median time of 20 days (9–41) without any influence of ALG use (97% vs 94% NS). Overall survival at 3 years was 45% in group 1 and 52% in group 2 (NS). The incidence of acute GvHD (grade II to IV) was similar in the two groups (59% vs 54%), but the incidence of acute GvHD (grade III to IV) was lower in group 1 (21% vs 32% p=0.03). Use of ALG did not affect rate relapse (18% vs 20% NS). In a multivariable analysis including HLA disparities, patient age, use of ALG, two factors appear as predictive for grade III–IV GvHD: HLA-identity (p=0.05) and use of ALG (p=0.02). These factors are not significant for survival in the same multivariable analysis but in this allelic matched population, the influence of ALG should be analyzed in regard of exact dose of ALG.