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 (150 mg/m2) and melphalan (140 mg/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.