 1.1. To evaluate the efficacy of allogeneic hematopoietic cell transplantation HCT in patients with acute lymphoblastic leukemia ALL either who have achieved complete remission CR after induction chemotherapy or who experienced recurrent leukemia then achieved second CR after salvage chemotherapy. The efficacy of the treatment will be measured in terms of the frequency of relapse after HCT and the duration of remission the primary endpoints. 