Grafts From HLA-Identical Siblings Versus HLA-Allelic-Matched Unrelated Donors (10/10) In Patients Undergoing Allogeneic Stem Cell Transplantation Following Reduced-Intensity Conditioning Regimen

Abstract 2380

Nonmyeloablative, or reduced-intensity conditioning (RIC), regimens before allo-SCT have emerged as an attractive modality to decrease transplant-related toxicity while preserving the graft-versus-tumor effect. However, as for standard myeloablative allo-CST, only one third of patients have an HLA-identical sibling donor. Indeed, with the increase in the number of single-child families, stem cell grafts from unrelated donors are being increasingly used.

We have previously reported, that in patients with standard-risk malignancy undergoing allo-SCT with CPM and TBI as conditioning treatment, unmodified marrow as a source of graft, and Cs-A plus short-course MTX as GVHD prophylaxis, there were no significant differences between the outcomes of patients receiving graft from siblings and those from unrelated fully HLA-matched donors (Yakoub-Agha et al, JCO 2006). However, no conclusions can be drawn with certainty concerning patients with more advanced disease, those who received a peripheral blood graft or especially those with a non-myeloablative conditioning regimen.

Here we report a retrospective study of 58 consecutive patients who received RIC allo-CST. Donors were HLA-identical sibling (n=35) and unrelated molecularly HLA-identical donor.

All donor/recipient pairs were typed at the allelic level. They were first typed at 2-digit level for HLA class I (HLA-A, B and Cw) and class II (HLA-DRB1 and DQB1) using published HLA class I PCR-SSO and/or SSP typing protocols. For unrelated donors, HLA-A, B, Cw, DRB1, B3, B4, B5 and DQB1 subtyping was performed using different PCR-SSP kits. HLA typing was performed according to the current use of the EFI Histocompatibility Laboratory standards. Only donor/recipient unrelated pairs matched for both alleles were included in this study.

Diagnosis were AML (n=27), ALL (n=3), myelodysplastic syndrome (n=13), and myeloproliferative syndrome (n=15). Of the 32 (55%) males patients, 14 (43%) received graft from female donor (classical sex-mismatch). Medians age of recipients and donors at transplantation were 58 years (41.3-65.5) and 47.1 years (22.2-67.5), respectively. Patients received either low-dose TBI (2Gy) (n=46) or Busulfan-based (n=12) conditioning regimen. Antithymoglobulin was given to 12 patients. As usual in RIC setting, Peripheral Blood Stem Cells was the main source of graft (n=38; 65%), otherwise marrow graft (n=20).