The Superiority of Allogeneic Hematopoietic Stem Cell Transplantation From Unrelated Donor Over Chemotherapy As Post-Remission Treatment for Patients with High-Risk Acute Lymphoblastic Leukemia in First Remission

Abstract 1986

For adult patients with acute lymphoblastic leukemia (ALL), allogeneic hematopoietic stem cell transplantation (allo-HSCT) from HLA-matched related donor (MSD) is recommended for standard and high-risk patients. The role of unrelated donor transplantation (URD) is not fully determined. In this single-center retrospective analysis, we included all consecutive adult patients with high-risk ALL in 1^st complete remission (CR) without sibling donor between Jan 2007 to June 2012. Overall, 74 patients were included in the analysis in which 32 patients received URD allo-HSCT during 1^st CR with busulfan-cyclophophamide preparation regimen and in vivo T cell depletion with anti-T-lymphoglobulin (ATG). The median time from remission to transplantation was 4.5 months (3∼13). Forty-two patients in the chemotherapy group with 1^st CR more than 6 months received consolidation chemotherapy alone either due to lack of suitable URD (n=21), refuse to URD search (n=14), unwillingness to undergo transplantation with available URD (n=5) and donor refuse to donate (n=2). Salvage allo-HSCT was allowed after relapse and actually 5 patients in the chemotherapy group received transplantation from URD donor (n=2) or haplo-identical donor (n=2) in the subsequent remission. The clinical characteristics such age, sex, initial WBC, and Philadelphia chromosome are all distributed equally in the two groups. With a median follow-up of 18 months for the whole group, 30 patients relapsed with estimated 3-year relapse rate (RR) at 58.1±8.5%. The 3-year event-free survival (LFS), non-relapse mortality (NRM) and overall survival (OS) were 38.0±7.9%, 11.1±4.4% and 46.0±9.0% respectively. In the URD allo-HSCT group, RR was 30.6±11.4% which was significantly lower than chemotherapy group (80.5±10.1%, p<0.001) while NRM was higher (16.4±6.7% vs. 0, p=0.028). Overall, 3-year LFS was superior in URD allo-HSCT group compared to chemotherapy (57.8±10.6% vs. 19.5±10.5%; median not reached vs. 13 months, p=0.002) and 3-year OS was also improved in URD allo-HSCT group (63.5±13.3%, median not reached versus 31.6±10.6%, median 24 months, p=0.016). Based on our data, URD allo-HSCT significantly reduced the relapse rate in high-risk ALL and the benefit translated into improvement in both LFS and OS. Prospective randomized study based on availability of HLA matched URD is warranted to confirm the exact role of URD transplantation in adult ALL.