In this prospective study, we examined the toxicity and efficacy of an 
intensified conditioning regimen for treatment of patients with relapsed or 
high-risk acute lymphoblastic leukemia who undergo allogeneic hematopoietic stem 
cell transplantation. Fifteen patients received fludarabine 30 mg/m(2), 
cytarabine 2000 mg/m(2), amsacrine 100 mg/m(2) on days -10, -9, -8 and -7, 
anti-thymocyte globulin (ATG-Fresenius) 20 mg/kg body weight on days -6, -5 and 
-4 and fractionated total body irradiation 2 x 2 Gy on days -3, -2 and -1 
(FLAMSA-ATG-TBI) before allogeneic hematopoietic stem cell transplantation. At 
the time of hematopoietic stem cell transplantation, 10 patients were in 
complete remission (8 CR1; 2 CR2), 3 with primary refractory and 2 suffered from 
refractory relapse. All patients achieved a complete remission after 
hematopoietic stem cell transplantation; and after a median follow-up time of 
1091 days (range, 334-1554 days), nine patients (60%) are alive and free from 
disease, including three patients with prior refractory disease. Three patients 
died due to treatment-related mortality. The most frequent and severe 
conditioning-related toxicities observed in 9 out of 15 patients were grade 
III/IV infections according to common toxicity criteria. Thus, conditioning with 
the FLAMSA-ATG-TBI regimen is a feasible and effective alternative for patients 
with relapsed or high-risk acute lymphoblastic leukemia.