Reduced-intensity conditioning allogeneic stem cell transplantation is a potential therapeutic approach for adults with high-risk acute lymphoblastic leukemia in remission: Results of a prospective phase 2 study

The aim of this prospective study was to investigate the feasibility of reduced-intensity conditioning (RIC) allogeneic stem cell transplantation (SCT) in 37 adults with high-risk acute lymphoblastic leukemia (ALL) in first (n=30) or second (n=7) complete remission (CR). All patients were treated with fludarabine (150mg/m²) and melphalan (140mg/m²) followed by transplantation from matched sibling (n=27) or unrelated (n=10) donors. The indications for reduced-intensity conditioning allogeneic SCT (RIC-SCT) were as follows: (1) ≥50 years, 16 (43.2%) and (2) decreased organ function or active infections, 21 (56.8%). Graft-versus-host disease (GVHD) prophylaxis consisted of calcineurin inhibitor (cyclosporine for sibling and tacrolimus for unrelated transplants) and methotrexate. The cumulative incidence of acute (grades II-IV) and chronic GVHD was 43.2 and 65.6%, respectively. After a median follow-up of 36 months for surviving transplants, the 3-year relapse, non-relapse mortality, disease-free survival and overall survival rates were 19.7, 17.7, 62.6 and 64.1%, respectively. Transplants in first CR showed better transplantation outcomes than those in second CR. The potential of antileukemic activity of chronic GVHD was also found. This study suggests that RIC-SCT is a potential therapeutic approach for adults with high-risk ALL in remission who are ineligible for myeloablative transplantation.