The use of bone marrow graft for haematopoietic stem cell transplantation from matched unrelated donors after reduced-intensity conditioning regimen improves survival: analysis of the Societe Francaise de Greffe de Moe Ile et de Therapie Cellulaire

Abstract Abstract 873 The use of peripheral blood stem cells (PBSC) for hematopoietic stem cell transplantation (HSCT) is associated with a higher risk of chronic graft versus host disease (GvHD) but its impact on survival is not clear since it may favor a greater graft versus leukemia (GvL) effect. However, in the context of HSCT from unrelated donors (UD), the balance between GvH and GvL may differ from the context of sibling donors and thus the use of PBSC may be deleterious. In this retrospective study, we analyzed 103 patients from the french registry who received a graft from an UD after a reduced intensity conditioning regimen (RIC) to evaluate the role of various parameters including the source of stem cells on the outcome. Seventy-one D/R pairs (69%) were 10/10 HLA match at the allelic level. Mismatches concerned 5, 6, 15, 2 and 7 D/R pairs for HLA-A, -B, -C, -DRB1 and -DQB1, respectively. The median age was 46 years (18-67). All patients had hematologic malignancies: AL (n=35), MM (n=18), CLL (n=5), NHL (n=11), HD (n=9), CML (n=12), MDS (n=9), and MPS (n=4). 39% of the patients were in an advanced phase of the disease at time of HSCT. The conditioning regimen was Fluda/TBI 2Gys for 26 patients, Bu/Fluda/ATG for 24 patients, Fluda/Melph for 16 patients and others for 37 patients. Overall, anti-thymocytes globulins (ATG) were part of the conditioning regimen for 77% of patients. The source of stem cells was PBSC for 65 patients and bone marrow (BM) for 38 patients. The median follow up of the cohort is 61,3 months (1,2-113,7). The results showed that 95% of patients engrafted. Five patients did not engraft (4 in the BM group and 1 in the PBSC group). Acute GvHD grade II to IV and grade III/IV occurred in 47% and 19% of patients, respectively. The risk of developing chronic GvHD was 49% at 2 years. Overall survival (OS) was 36% at five years. The median disease free survival (DFS) was 55 months among the 36 patients alive. We performed univariate and multivariate analysis of factors susceptible to impact on GvHD and survival. The multivariate analysis included the impact of HLA mismatch, disease status, diagnosis, source of stem cells, patient's and donor's ages. This multivariate analysis performed on the global population shows a trend towards an improved OS with the use of BM instead of PBSC. However, when focusing the multivariate analysis on the 71 patients transplanted with a 10/10 match donor, the most potent factor influencing the outcome is the use of BM which is associated with an improved OS (p=0.03) and DFS (p=0.02), less acute GvHD grade II-IV (p=0.05), or grade III/IV (p=0.05) and less chronic GvHD (p=0.05). These results suggest that the use of BM as the source of stem cells should be reconsidered in the context of matched UD after RIC transplantation. Disclosures: No relevant conflicts of interest to declare.