Hematopoietic cell transplantation in acute lymphoblastic leukemia: betterlong-term event-free survival with conditioning regimens containing total body irradiation

Background and Objectives. There is only limited experience with conditioni ng regimens based on busulfan for patients with acute lymphoblastic leukemi a (ALL). Therefore, the aim of this study was to compare the event-free sur vival (EFS), transplant-related mortality (TRM) and the probability of rela pse (PR) of patients undergoing hematopoietic cell transplantation (HCT) fo r ALL conditioned with or without total body irradiation (TBI). Design and Methods. The study sample consisted of 156 patients conditioned with regimens based on TBI (n=114) or on high doses of oral busulfan (BU) ( n=42). Most of the BU group received phenytoin as prophylaxis for seizures. The median follow-up was 6 years. Results. EFS at 6 years was 43% (95% CI 35%-51%) versus 22% (95% CI 10%-34% ) in the TBI and BU subsets, respectively (p=0.01). TRM at 18 months was 22 % and 17% in the BU and TBI groups (p=0.24), respectively. At 3 years actua rial PR was 71% in the BU group and 47% in the TBI group (p=0.01). In the m ultivariable analysis, a worse EFS was associated with BU, relative risk (R R) 1.7; advanced disease versus 1st and 2nd complete remission (CR) at HCT, RR 2.5; absence of chronic graft-versus-host disease, RR 1.8; development of veno-occlusive disease RR 2.2 and shorter CR duration before transplant. Interpretation and Conclusions. TBI was associated with a lower relapse rat e and better EFS, even in patients in 1(st) and 2(nd) CR, than schemes base d on high doses of busulfan. This suggests that conditioning regimens based on TBI should remain the standard method of preparative regimen far patien ts with ALL. (C)2000, Ferrata Storti Foundation.