A Safety and Efficacy Study of Medium-Dose Etoposide, Cyclophosphamide and Total Body Irradiation Conditioning before Allogeneic Stem Cell Transplantation for Acute Lymphoblastic Leukemia

Background. Prognosis for adult patients with acute lymphoblastic leukemia (ALL) has been reported to be approximately 35% to 50%, even after allogeneic stem cell transplantation (allo-SCT). We previously reported retrospective analyses of a conditioning regimen of medium-dose etoposide, cyclophosphamide (CY), and total body irradiation (TBI) before allo-SCT for ALL. To prospectively analyze the efficacy of this conditioning regimen, we conducted a trial prospectively. Methods. The eligibility criteria of this study were as follows: diagnosis of ALL, aged between 15 and 50 years, in complete remission, and first SCT from HLA serologically matched donor. The primary endpoint of this study was event-free survival at 1 year after SCT, and the events were defined as death and relapse. Results. Fifty eligible patients were treated, and the median age of the patients was 33.5 years. Nineteen patients were Philadelphia chromosome-positive, and 47 were in first complete remission at SCT. All patients achieved neutrophil engraftment. Grade 3 to 4 acute graft-versus-host disease and extensive chronic graft-versus-host disease developed in 4 patients and 18 patients, respectively. No patient died within 100 days after SCT. One-year event-free survival was 76.0%, and 1-year overall survival was 80.0%. The cumulative incidences of relapse and non-relapse mortality at 1-year after SCT were 10.0% and 14.0%, respectively. Conclusions. Medium-dose etoposide + CY + TBI is an effective conditioning before allo-SCT for adult patients with ALL, enabling good disease control without an increase in nonrelapse mortality. A phase 3 trial comparing this regimen with the standard CY + TBI regimen for adult patients with ALL is warranted.