The superiority of allogeneic hematopoietic stem cell transplantation from unrelated donor over chemotherapy for adult patients with high-risk acute lymphoblastic leukemia in first remission.

For adult patients with acute lymphoblastic leukemia (ALL), allogeneic hematopoietic stem cell transplantation(allo-HSCT) from HLA-matched related donors(MSD) is recommended for standard and high-risk patients. The role of unrelated donor transplantation (URD) in first remission has not been fully determined. We sought to compare directly the outcome of URD allo-HSCT and chemotherapy in patients with high-risk ALL. In this single center retrospective analysis, we included 74 consecutive adult patients with high-risk ALL in first complete remission(CR) and without a sibling donor, in which 32 patients received URD allo-HSCT in CR1 with busulfan-cyclophosphamide preparation regimen and in vivo T-cell depletion with anti-T-lymphoglobulin (ATG). The remaining 42 patients received chemotherapy consolidation and maintenance only in first remission. With median follow-up of 18 months, in the URD allo-HSCT group, the relapse rate(RR) was 30.6 ± 11.4 % which was significantly lower than that of the chemotherapy group (80.5 ± 10.1 %,p < 0.001), while non-relapse mortality (NRM) was higher(16.4 ± 6.7 % vs. 0, p = 0.028). Overall, 3-year leukemia free survival (LFS) was superior in the URD allo-HSCT group compared to chemotherapy group (57.8 ± 10.6 vs.19.5 ± 10.5 %, p = 0.002), as was 3-year overall survival(OS, 63.5 ± 13.3 vs. 31.6 ± 10.6 %, p = 0.016). URDHSCT was the only factor associated with improved OS, LFS and reduced RR in multivariate analysis. Based on our data, URD allo-HSCT significantly reduced the relapse in high-risk ALL and the benefit translated into improvement in both LFS and OS. Prospective studies based on availability of HLA-matched URD are warranted to evaluate the precise role of URD transplantation in adult ALL.