Unrelated Allogeneic Stem Cell Transplantation with Myeloablative Preparative Regimen for Adult Patients with Acute Lymphoblastic Leukemia in CR: A Survey from the European Group for Blood and Marrow Transplantation (EBMT).

Data from the EBMT indicate that approximately 46% of Unrelated Allogeneic Stem Cell Transplantation (UD-SCT) in Europe utilize peripheral blood (PB) and 54% bone marrow (BM) as a graft source for adult patients with ALL since January 1998. However, prospective randomized trials comparing the two stem cell sources are lacking. This study describes the results of 782 adult patients with ALL in remission (422 BM and 360 PB) transplanted in different centers affiliated with the EBMT from 1998 to 2004 with an HLA identical unrelated donor (HLA-A and -B low resolution and HLA-DRB1 allelic typing). Median age was 27 years for BM (range 16–63, male 60%) and 30 years for PB (range16–63, male 62%), respectively. Fifty four (54%) and 64% of patients were transplanted in first complete remission (CR1) in the BM and PB groups, respectively. The frequency of female donor to male recipient was 18% in the BM and 15% in the PB group. Total Body Irradiation (TBI)-based preparative regimens were given in 85% and 88% of patients in the BM and PB group respectively. Graft-versus-Host Disease (GvHD) prophylaxis consisted of cyclosporine A (CsA) (6% and 4%), CsA and methotrexate (77% and 58%) or in vitroT-cell depletion (17% and 38% in BM and PB group, respectively). With the median follow-up of 17 (range 1–92) and 11,3 (range 1–71) months, the incidence of GvHD grade II–IV was 37% in the BM group and 39% in the PB group (p=0.39). Probabilities of LFS, TRM and relapse were calculated using the Kaplan-Meier estimate. LFS was 45+/−3% vs 36+/−3% (p=0.04) transplant related mortality (TRM) was 33+/−2% and 39+/−3(p=0.29 while incidence of relapse was 32+/−3% and 41+/−4%(p=0.06), in the BM and PB groups respectively. Two years leukemia-free survival (LFS) for the patients transplanted in CR1 was 48% (BM) and 42% (PB, p=0.48). However, 2-years LFS for patients transplanted in CR2 or CR3 was significantly higher in the BM compared to the PB group (42% and 26%, p<0.004). The probability of relapse was significantly lower in BM compared to PB (32% vs 54%, p<0.001) without there being a detectable difference in TRM at 2 years (38% vs 43%, p= 0.31).

In conclusion, the results of this retrospective comparative study confirm that UD-SCT with BM and PB as a graft source have similar results for patients in CR1. However, patients transplanted in CR2 or CR3 with a bone marrow graft, have decreased relapse incidence and better LFS, probably reflecting disease and transplant related differences compared to PB transplants such as in vitro T cell depletion more used in those transplants.